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 $194.97   8.200%   $210.9575   $210.96   $210.95   $211.00  
  Purchase #2 $42.88   6.613%   $45.7157   $45.72   $45.70   $45.70  
  Purchase #3 $247.67   9.633%   $271.5281   $271.53   $271.55   $271.50  
  Purchase #4 $62.75   13.757%   $71.3825   $71.38   $71.40   $71.40  
  Purchase #5 $208.95   12.503%   $235.075   $235.08   $235.10   $235.10  
  Purchase #6 $190.55   7.227%   $204.321   $204.32   $204.30   $204.30  
  Purchase #7 $68.48   4.181%   $71.3431   $71.34   $71.35   $71.30  
  7 purchase totals = $1,016.25       $1,110.3229   $1,110.33   $1,110.35   $1,110.30