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 $215.96   3.853%   $224.2809   $224.28   $224.30   $224.30  
  Purchase #2 $44.99   13.241%   $50.9471   $50.95   $50.95   $50.90  
  Purchase #3 $248.67   7.867%   $268.2329   $268.23   $268.25   $268.20  
  Purchase #4 $43.95   11.654%   $49.0719   $49.07   $49.05   $49.10  
  Purchase #5 $187.93   11.263%   $209.0966   $209.10   $209.10   $209.10  
  Purchase #6 $166.67   7.109%   $178.5186   $178.52   $178.50   $178.50  
  Purchase #7 $247.49   11.502%   $275.9563   $275.96   $275.95   $276.00  
  7 purchase totals = $1,155.66       $1,256.1043   $1,256.11   $1,256.10   $1,256.10