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 $182.75   6.692%   $194.9796   $194.98   $195.00   $195.00  
  Purchase #2 $205.58   13.305%   $232.9324   $232.93   $232.95   $232.90  
  Purchase #3 $173.90   8.598%   $188.8519   $188.85   $188.85   $188.90  
  Purchase #4 $67.55   8.322%   $73.1715   $73.17   $73.15   $73.20  
  Purchase #5 $26.63   7.589%   $28.651   $28.65   $28.65   $28.70  
  Purchase #6 $7.82   12.807%   $8.8215   $8.82   $8.80   $8.80  
  Purchase #7 $9.95   8.446%   $10.7904   $10.79   $10.80   $10.80  
  7 purchase totals = $674.18       $738.1983   $738.19   $738.20   $738.30