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 $211.77   11.122%   $235.3231   $235.32   $235.30   $235.30  
  Purchase #2 $146.98   10.649%   $162.6319   $162.63   $162.65   $162.60  
  Purchase #3 $91.26   3.505%   $94.4587   $94.46   $94.45   $94.50  
  Purchase #4 $201.62   6.425%   $214.5741   $214.57   $214.55   $214.60  
  Purchase #5 $197.50   11.265%   $219.7484   $219.75   $219.75   $219.70  
  Purchase #6 $184.32   13.488%   $209.1811   $209.18   $209.20   $209.20  
  Purchase #7 $25.61   4.267%   $26.7028   $26.70   $26.70   $26.70  
  7 purchase totals = $1,059.06       $1,162.6201   $1,162.61   $1,162.60   $1,162.60