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 $60.95   10.195%   $67.1639   $67.16   $67.15   $67.20  
  Purchase #2 $124.27   4.333%   $129.6546   $129.65   $129.65   $129.70  
  Purchase #3 $219.65   11.316%   $244.5056   $244.51   $244.50   $244.50  
  Purchase #4 $249.78   4.489%   $260.9926   $260.99   $261.00   $261.00  
  Purchase #5 $182.72   6.217%   $194.0797   $194.08   $194.10   $194.10  
  Purchase #6 $73.61   5.169%   $77.4149   $77.41   $77.40   $77.40  
  Purchase #7 $55.98   4.696%   $58.6088   $58.61   $58.60   $58.60  
  7 purchase totals = $966.96       $1,032.4201   $1,032.41   $1,032.40   $1,032.50