Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $113.92   8.804%   $123.9495   $123.95   $123.95   $123.90  
  Purchase #2 $219.80   12.354%   $246.9541   $246.95   $246.95   $247.00  
  Purchase #3 $216.65   4.646%   $226.7156   $226.72   $226.70   $226.70  
  Purchase #4 $165.91   13.109%   $187.6591   $187.66   $187.65   $187.70  
  Purchase #5 $187.75   11.358%   $209.0746   $209.07   $209.05   $209.10  
  Purchase #6 $216.85   3.475%   $224.3855   $224.39   $224.40   $224.40  
  Purchase #7 $204.54   9.398%   $223.7627   $223.76   $223.75   $223.80  
  7 purchase totals = $1,325.42       $1,442.5011   $1,442.50   $1,442.45   $1,442.60