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 $89.95   5.672%   $95.052   $95.05   $95.05   $95.10  
  Purchase #2 $247.58   5.227%   $260.521   $260.52   $260.50   $260.50  
  Purchase #3 $217.26   8.256%   $235.197   $235.20   $235.20   $235.20  
  Purchase #4 $5.66   8.113%   $6.1192   $6.12   $6.10   $6.10  
  Purchase #5 $94.30   9.599%   $103.3519   $103.35   $103.35   $103.40  
  Purchase #6 $63.43   4.363%   $66.1975   $66.20   $66.20   $66.20  
  Purchase #7 $201.80   11.808%   $225.6285   $225.63   $225.65   $225.60  
  7 purchase totals = $919.98       $992.0671   $992.07   $992.05   $992.10