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 $70.86   4.404%   $73.9807   $73.98   $74.00   $74.00  
  Purchase #2 $26.48   10.694%   $29.3118   $29.31   $29.30   $29.30  
  Purchase #3 $56.28   6.617%   $60.004   $60.00   $60.00   $60.00  
  Purchase #4 $94.32   8.242%   $102.0939   $102.09   $102.10   $102.10  
  Purchase #5 $40.53   3.367%   $41.8946   $41.89   $41.90   $41.90  
  Purchase #6 $194.87   7.541%   $209.5651   $209.57   $209.55   $209.60  
  Purchase #7 $250.37   5.706%   $264.6561   $264.66   $264.65   $264.70  
  7 purchase totals = $733.71       $781.5062   $781.50   $781.50   $781.60