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 $87.84   8.176%   $95.0218   $95.02   $95.00   $95.00  
  Purchase #2 $182.54   9.368%   $199.6403   $199.64   $199.65   $199.60  
  Purchase #3 $157.51   9.218%   $172.0293   $172.03   $172.05   $172.00  
  Purchase #4 $24.96   8.629%   $27.1138   $27.11   $27.10   $27.10  
  Purchase #5 $13.61   10.492%   $15.038   $15.04   $15.05   $15.00  
  Purchase #6 $217.84   12.446%   $244.9524   $244.95   $244.95   $245.00  
  Purchase #7 $54.65   6.340%   $58.1148   $58.11   $58.10   $58.10  
  7 purchase totals = $738.95       $811.9104   $811.90   $811.90   $811.80