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 $83.75   13.660%   $95.1903   $95.19   $95.20   $95.20  
  Purchase #2 $67.67   5.472%   $71.3729   $71.37   $71.35   $71.40  
  Purchase #3 $195.70   12.413%   $219.9922   $219.99   $220.00   $220.00  
  Purchase #4 $84.74   12.369%   $95.2215   $95.22   $95.20   $95.20  
  Purchase #5 $58.80   13.833%   $66.9338   $66.93   $66.95   $66.90  
  Purchase #6 $162.50   9.552%   $178.022   $178.02   $178.00   $178.00  
  Purchase #7 $5.31   8.334%   $5.7525   $5.75   $5.75   $5.80  
  7 purchase totals = $658.47       $732.4852   $732.47   $732.45   $732.50