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 $114.59   9.585%   $125.5735   $125.57   $125.55   $125.60  
  Purchase #2 $78.44   11.128%   $87.1688   $87.17   $87.15   $87.20  
  Purchase #3 $236.47   11.279%   $263.1415   $263.14   $263.15   $263.10  
  Purchase #4 $41.45   5.152%   $43.5855   $43.59   $43.60   $43.60  
  Purchase #5 $227.41   11.350%   $253.221   $253.22   $253.20   $253.20  
  Purchase #6 $56.42   4.482%   $58.9487   $58.95   $58.95   $58.90  
  Purchase #7 $184.75   10.812%   $204.7252   $204.73   $204.75   $204.70  
  7 purchase totals = $939.53       $1,036.3642   $1,036.37   $1,036.35   $1,036.30