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 $54.43   9.788%   $59.7576   $59.76   $59.75   $59.80  
  Purchase #2 $227.47   9.413%   $248.8818   $248.88   $248.90   $248.90  
  Purchase #3 $178.31   4.584%   $186.4837   $186.48   $186.50   $186.50  
  Purchase #4 $145.96   6.470%   $155.4036   $155.40   $155.40   $155.40  
  Purchase #5 $184.93   5.181%   $194.5112   $194.51   $194.50   $194.50  
  Purchase #6 $154.96   3.657%   $160.6269   $160.63   $160.65   $160.60  
  Purchase #7 $148.30   8.744%   $161.2674   $161.27   $161.25   $161.30  
  7 purchase totals = $1,094.36       $1,166.9322   $1,166.93   $1,166.95   $1,167.00