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 $60.92   3.577%   $63.0991   $63.10   $63.10   $63.10  
  Purchase #2 $227.96   11.610%   $254.4262   $254.43   $254.45   $254.40  
  Purchase #3 $194.97   7.437%   $209.4699   $209.47   $209.45   $209.50  
  Purchase #4 $169.67   4.574%   $177.4307   $177.43   $177.45   $177.40  
  Purchase #5 $204.64   3.596%   $211.9989   $212.00   $212.00   $212.00  
  Purchase #6 $102.62   4.813%   $107.5591   $107.56   $107.55   $107.60  
  Purchase #7 $224.45   5.420%   $236.6152   $236.62   $236.60   $236.60  
  7 purchase totals = $1,185.23       $1,260.5991   $1,260.61   $1,260.60   $1,260.60