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 $247.82   7.728%   $266.9715   $266.97   $266.95   $267.00  
  Purchase #2 $42.37   6.659%   $45.1914   $45.19   $45.20   $45.20  
  Purchase #3 $159.57   4.675%   $167.0299   $167.03   $167.05   $167.00  
  Purchase #4 $242.88   9.741%   $266.5389   $266.54   $266.55   $266.50  
  Purchase #5 $200.74   10.258%   $221.3319   $221.33   $221.35   $221.30  
  Purchase #6 $15.48   6.690%   $16.5156   $16.52   $16.50   $16.50  
  Purchase #7 $250.84   7.545%   $269.7659   $269.77   $269.75   $269.80  
  7 purchase totals = $1,159.70       $1,253.3451   $1,253.35   $1,253.35   $1,253.30