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 $206.58   13.253%   $233.958   $233.96   $233.95   $234.00  
  Purchase #2 $215.40   9.451%   $235.7575   $235.76   $235.75   $235.80  
  Purchase #3 $45.49   13.419%   $51.5943   $51.59   $51.60   $51.60  
  Purchase #4 $166.58   9.430%   $182.2885   $182.29   $182.30   $182.30  
  Purchase #5 $225.50   8.102%   $243.77   $243.77   $243.75   $243.80  
  Purchase #6 $29.76   8.529%   $32.2982   $32.30   $32.30   $32.30  
  Purchase #7 $201.43   7.843%   $217.2282   $217.23   $217.25   $217.20  
  7 purchase totals = $1,090.74       $1,196.8947   $1,196.90   $1,196.90   $1,197.00