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 $214.36   10.613%   $237.11   $237.11   $237.10   $237.10  
  Purchase #2 $16.33   3.693%   $16.9331   $16.93   $16.95   $16.90  
  Purchase #3 $46.30   4.535%   $48.3997   $48.40   $48.40   $48.40  
  Purchase #4 $198.83   6.772%   $212.2948   $212.29   $212.30   $212.30  
  Purchase #5 $104.42   12.814%   $117.8004   $117.80   $117.80   $117.80  
  Purchase #6 $22.54   13.133%   $25.5002   $25.50   $25.50   $25.50  
  Purchase #7 $203.54   3.240%   $210.1347   $210.13   $210.15   $210.10  
  7 purchase totals = $806.32       $868.1729   $868.16   $868.20   $868.10