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 $141.80   7.197%   $152.0053   $152.01   $152.00   $152.00  
  Purchase #2 $218.29   10.327%   $240.8328   $240.83   $240.85   $240.80  
  Purchase #3 $154.88   8.230%   $167.6266   $167.63   $167.65   $167.60  
  Purchase #4 $244.27   8.313%   $264.5762   $264.58   $264.60   $264.60  
  Purchase #5 $163.75   10.306%   $180.6261   $180.63   $180.65   $180.60  
  Purchase #6 $58.53   7.237%   $62.7658   $62.77   $62.75   $62.80  
  Purchase #7 $46.29   7.150%   $49.5997   $49.60   $49.60   $49.60  
  7 purchase totals = $1,027.81       $1,118.0325   $1,118.05   $1,118.10   $1,118.00