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 $62.28   5.742%   $65.8561   $65.86   $65.85   $65.90  
  Purchase #2 $235.33   13.205%   $266.4053   $266.41   $266.40   $266.40  
  Purchase #3 $44.71   3.337%   $46.202   $46.20   $46.20   $46.20  
  Purchase #4 $12.87   5.500%   $13.5779   $13.58   $13.60   $13.60  
  Purchase #5 $197.57   11.625%   $220.5375   $220.54   $220.55   $220.50  
  Purchase #6 $229.44   7.355%   $246.3153   $246.32   $246.30   $246.30  
  Purchase #7 $24.65   5.865%   $26.0957   $26.10   $26.10   $26.10  
  7 purchase totals = $806.85       $884.9898   $885.01   $885.00   $885.00