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 $182.52   6.543%   $194.4623   $194.46   $194.45   $194.50  
  Purchase #2 $212.61   9.486%   $232.7782   $232.78   $232.80   $232.80  
  Purchase #3 $163.57   7.326%   $175.5531   $175.55   $175.55   $175.60  
  Purchase #4 $69.30   9.183%   $75.6638   $75.66   $75.65   $75.70  
  Purchase #5 $232.70   6.250%   $247.2438   $247.24   $247.25   $247.20  
  Purchase #6 $119.92   10.864%   $132.9481   $132.95   $132.95   $132.90  
  Purchase #7 $189.87   7.242%   $203.6204   $203.62   $203.60   $203.60  
  7 purchase totals = $1,170.49       $1,262.2697   $1,262.26   $1,262.25   $1,262.30