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 $86.33   11.258%   $96.049   $96.05   $96.05   $96.00  
  Purchase #2 $69.35   7.823%   $74.7753   $74.78   $74.80   $74.80  
  Purchase #3 $132.43   8.809%   $144.0958   $144.10   $144.10   $144.10  
  Purchase #4 $39.46   6.216%   $41.9128   $41.91   $41.90   $41.90  
  Purchase #5 $222.59   4.635%   $232.907   $232.91   $232.90   $232.90  
  Purchase #6 $84.69   11.854%   $94.7292   $94.73   $94.75   $94.70  
  Purchase #7 $125.37   13.143%   $141.8474   $141.85   $141.85   $141.80  
  7 purchase totals = $760.22       $826.3165   $826.33   $826.35   $826.20