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 $92.50   3.548%   $95.7819   $95.78   $95.80   $95.80  
  Purchase #2 $199.26   4.249%   $207.7266   $207.73   $207.75   $207.70  
  Purchase #3 $220.96   7.157%   $236.7741   $236.77   $236.75   $236.80  
  Purchase #4 $218.89   9.340%   $239.3343   $239.33   $239.35   $239.30  
  Purchase #5 $197.47   5.866%   $209.0536   $209.05   $209.05   $209.10  
  Purchase #6 $28.32   3.506%   $29.3129   $29.31   $29.30   $29.30  
  Purchase #7 $11.26   11.190%   $12.52   $12.52   $12.50   $12.50  
  7 purchase totals = $968.66       $1,030.5034   $1,030.49   $1,030.50   $1,030.50