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 $61.56   10.529%   $68.0417   $68.04   $68.05   $68.00  
  Purchase #2 $174.43   5.557%   $184.1231   $184.12   $184.10   $184.10  
  Purchase #3 $116.36   7.639%   $125.2487   $125.25   $125.25   $125.20  
  Purchase #4 $233.33   4.365%   $243.5149   $243.51   $243.50   $243.50  
  Purchase #5 $146.40   7.554%   $157.4591   $157.46   $157.45   $157.50  
  Purchase #6 $166.71   12.431%   $187.4337   $187.43   $187.45   $187.40  
  Purchase #7 $122.30   10.805%   $135.5145   $135.51   $135.50   $135.50  
  7 purchase totals = $1,021.09       $1,101.3357   $1,101.32   $1,101.30   $1,101.20