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 $58.86   3.795%   $61.0937   $61.09   $61.10   $61.10  
  Purchase #2 $219.37   10.772%   $243.0005   $243.00   $243.00   $243.00  
  Purchase #3 $48.85   3.589%   $50.6032   $50.60   $50.60   $50.60  
  Purchase #4 $83.73   11.751%   $93.5691   $93.57   $93.55   $93.60  
  Purchase #5 $78.95   10.115%   $86.9358   $86.94   $86.95   $86.90  
  Purchase #6 $90.25   4.479%   $94.2923   $94.29   $94.30   $94.30  
  Purchase #7 $225.55   4.707%   $236.1666   $236.17   $236.15   $236.20  
  7 purchase totals = $805.56       $865.6612   $865.66   $865.65   $865.70