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 $42.94   8.472%   $46.5779   $46.58   $46.60   $46.60  
  Purchase #2 $214.37   6.192%   $227.6438   $227.64   $227.65   $227.60  
  Purchase #3 $9.83   9.178%   $10.7322   $10.73   $10.75   $10.70  
  Purchase #4 $93.64   5.814%   $99.0842   $99.08   $99.10   $99.10  
  Purchase #5 $100.28   4.502%   $104.7946   $104.79   $104.80   $104.80  
  Purchase #6 $55.66   11.381%   $61.9947   $61.99   $62.00   $62.00  
  Purchase #7 $210.27   3.220%   $217.0407   $217.04   $217.05   $217.00  
  7 purchase totals = $726.99       $767.8681   $767.85   $767.95   $767.80