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 $153.32   9.607%   $168.0495   $168.05   $168.05   $168.00  
  Purchase #2 $189.30   11.231%   $210.5603   $210.56   $210.55   $210.60  
  Purchase #3 $149.47   11.442%   $166.5724   $166.57   $166.55   $166.60  
  Purchase #4 $66.63   11.654%   $74.3951   $74.40   $74.40   $74.40  
  Purchase #5 $240.78   3.558%   $249.347   $249.35   $249.35   $249.30  
  Purchase #6 $141.57   9.781%   $155.417   $155.42   $155.40   $155.40  
  Purchase #7 $221.66   7.252%   $237.7348   $237.73   $237.75   $237.70  
  7 purchase totals = $1,162.73       $1,262.0761   $1,262.08   $1,262.05   $1,262.00