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 $58.64   4.226%   $61.1181   $61.12   $61.10   $61.10  
  Purchase #2 $212.65   8.143%   $229.9661   $229.97   $229.95   $230.00  
  Purchase #3 $92.50   11.552%   $103.1856   $103.19   $103.20   $103.20  
  Purchase #4 $144.59   4.709%   $151.3987   $151.40   $151.40   $151.40  
  Purchase #5 $180.57   11.126%   $200.6602   $200.66   $200.65   $200.70  
  Purchase #6 $150.73   8.681%   $163.8149   $163.81   $163.80   $163.80  
  Purchase #7 $41.51   5.645%   $43.8532   $43.85   $43.85   $43.90  
  7 purchase totals = $881.19       $953.9968   $954.00   $953.95   $954.10