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 $63.40   13.499%   $71.9584   $71.96   $71.95   $72.00  
  Purchase #2 $168.33   7.376%   $180.746   $180.75   $180.75   $180.70  
  Purchase #3 $154.47   5.680%   $163.2439   $163.24   $163.25   $163.20  
  Purchase #4 $154.81   7.688%   $166.7118   $166.71   $166.70   $166.70  
  Purchase #5 $243.52   10.263%   $268.5125   $268.51   $268.50   $268.50  
  Purchase #6 $243.28   8.415%   $263.752   $263.75   $263.75   $263.80  
  Purchase #7 $24.42   7.452%   $26.2398   $26.24   $26.25   $26.20  
  7 purchase totals = $1,052.23       $1,141.1644   $1,141.16   $1,141.15   $1,141.10