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 $216.52   5.187%   $227.7509   $227.75   $227.75   $227.80  
  Purchase #2 $65.28   3.336%   $67.4577   $67.46   $67.45   $67.50  
  Purchase #3 $184.37   7.217%   $197.676   $197.68   $197.70   $197.70  
  Purchase #4 $93.94   9.676%   $103.0296   $103.03   $103.05   $103.00  
  Purchase #5 $16.25   11.566%   $18.1295   $18.13   $18.15   $18.10  
  Purchase #6 $234.86   8.252%   $254.2406   $254.24   $254.25   $254.20  
  Purchase #7 $130.76   10.141%   $144.0204   $144.02   $144.00   $144.00  
  7 purchase totals = $941.98       $1,012.3047   $1,012.31   $1,012.35   $1,012.30