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 $56.29   7.674%   $60.6097   $60.61   $60.60   $60.60  
  Purchase #2 $187.62   3.815%   $194.7777   $194.78   $194.80   $194.80  
  Purchase #3 $217.29   6.293%   $230.9641   $230.96   $230.95   $231.00  
  Purchase #4 $128.91   5.115%   $135.5037   $135.50   $135.50   $135.50  
  Purchase #5 $52.92   7.656%   $56.9716   $56.97   $56.95   $57.00  
  Purchase #6 $238.82   4.608%   $249.8248   $249.82   $249.80   $249.80  
  Purchase #7 $32.34   6.692%   $34.5042   $34.50   $34.50   $34.50  
  7 purchase totals = $914.19       $963.1558   $963.14   $963.10   $963.20