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 $87.43   8.259%   $94.6508   $94.65   $94.65   $94.70  
  Purchase #2 $202.76   13.696%   $230.53   $230.53   $230.55   $230.50  
  Purchase #3 $151.27   8.363%   $163.9207   $163.92   $163.90   $163.90  
  Purchase #4 $71.35   5.253%   $75.098   $75.10   $75.10   $75.10  
  Purchase #5 $152.30   11.455%   $169.746   $169.75   $169.75   $169.70  
  Purchase #6 $201.83   13.808%   $229.6987   $229.70   $229.70   $229.70  
  Purchase #7 $206.45   6.238%   $219.3284   $219.33   $219.35   $219.30  
  7 purchase totals = $1,073.39       $1,182.9726   $1,182.98   $1,183.00   $1,182.90