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 $162.39   7.835%   $175.1133   $175.11   $175.10   $175.10  
  Purchase #2 $233.33   8.158%   $252.3651   $252.37   $252.35   $252.40  
  Purchase #3 $53.76   11.175%   $59.7677   $59.77   $59.75   $59.80  
  Purchase #4 $156.85   5.363%   $165.2619   $165.26   $165.25   $165.30  
  Purchase #5 $98.31   3.138%   $101.395   $101.40   $101.40   $101.40  
  Purchase #6 $152.88   6.463%   $162.7606   $162.76   $162.75   $162.80  
  Purchase #7 $95.90   12.390%   $107.782   $107.78   $107.80   $107.80  
  7 purchase totals = $953.42       $1,024.4456   $1,024.45   $1,024.40   $1,024.60