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 $59.79   5.873%   $63.3015   $63.30   $63.30   $63.30  
  Purchase #2 $54.62   8.508%   $59.2671   $59.27   $59.25   $59.30  
  Purchase #3 $200.48   7.646%   $215.8087   $215.81   $215.80   $215.80  
  Purchase #4 $180.86   12.488%   $203.4458   $203.45   $203.45   $203.40  
  Purchase #5 $169.94   9.425%   $185.9568   $185.96   $185.95   $186.00  
  Purchase #6 $230.33   10.700%   $254.9753   $254.98   $255.00   $255.00  
  Purchase #7 $175.84   10.385%   $194.101   $194.10   $194.10   $194.10  
  7 purchase totals = $1,071.86       $1,176.8562   $1,176.87   $1,176.85   $1,176.90