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 $86.84   10.464%   $95.9269   $95.93   $95.95   $95.90  
  Purchase #2 $12.96   3.394%   $13.3999   $13.40   $13.40   $13.40  
  Purchase #3 $243.42   10.718%   $269.5098   $269.51   $269.50   $269.50  
  Purchase #4 $137.30   10.448%   $151.6451   $151.65   $151.65   $151.60  
  Purchase #5 $146.44   11.312%   $163.0053   $163.01   $163.00   $163.00  
  Purchase #6 $187.63   11.587%   $209.3707   $209.37   $209.35   $209.40  
  Purchase #7 $230.28   13.261%   $260.8174   $260.82   $260.80   $260.80  
  7 purchase totals = $1,044.87       $1,163.6751   $1,163.69   $1,163.65   $1,163.60