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 $22.66   11.301%   $25.2208   $25.22   $25.20   $25.20  
  Purchase #2 $244.41   10.212%   $269.3691   $269.37   $269.35   $269.40  
  Purchase #3 $40.52   13.170%   $45.8565   $45.86   $45.85   $45.90  
  Purchase #4 $194.63   4.767%   $203.908   $203.91   $203.90   $203.90  
  Purchase #5 $250.53   5.193%   $263.54   $263.54   $263.55   $263.50  
  Purchase #6 $178.44   9.747%   $195.8325   $195.83   $195.85   $195.80  
  Purchase #7 $92.42   6.567%   $98.4892   $98.49   $98.50   $98.50  
  7 purchase totals = $1,023.61       $1,102.2161   $1,102.22   $1,102.20   $1,102.20