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 $87.37   12.872%   $98.6163   $98.62   $98.60   $98.60  
  Purchase #2 $92.77   5.149%   $97.5467   $97.55   $97.55   $97.50  
  Purchase #3 $125.98   5.690%   $133.1483   $133.15   $133.15   $133.10  
  Purchase #4 $55.47   9.402%   $60.6853   $60.69   $60.70   $60.70  
  Purchase #5 $29.98   10.711%   $33.1912   $33.19   $33.20   $33.20  
  Purchase #6 $162.79   5.849%   $172.3116   $172.31   $172.30   $172.30  
  Purchase #7 $141.97   10.282%   $156.5674   $156.57   $156.55   $156.60  
  7 purchase totals = $696.33       $752.0668   $752.08   $752.05   $752.00