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 $92.93   3.310%   $96.006   $96.01   $96.00   $96.00  
  Purchase #2 $78.31   13.117%   $88.5819   $88.58   $88.60   $88.60  
  Purchase #3 $57.80   7.560%   $62.1697   $62.17   $62.15   $62.20  
  Purchase #4 $26.58   6.282%   $28.2498   $28.25   $28.25   $28.20  
  Purchase #5 $125.57   6.659%   $133.9317   $133.93   $133.95   $133.90  
  Purchase #6 $236.57   6.245%   $251.3438   $251.34   $251.35   $251.30  
  Purchase #7 $41.33   12.358%   $46.4376   $46.44   $46.45   $46.40  
  7 purchase totals = $659.09       $706.7205   $706.72   $706.75   $706.60