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 $51.33   5.113%   $53.9545   $53.95   $53.95   $54.00  
  Purchase #2 $130.36   4.323%   $135.9955   $136.00   $136.00   $136.00  
  Purchase #3 $105.84   6.579%   $112.8032   $112.80   $112.80   $112.80  
  Purchase #4 $196.33   5.369%   $206.871   $206.87   $206.85   $206.90  
  Purchase #5 $188.94   13.199%   $213.8782   $213.88   $213.90   $213.90  
  Purchase #6 $184.47   10.348%   $203.559   $203.56   $203.55   $203.60  
  Purchase #7 $17.46   4.117%   $18.1788   $18.18   $18.20   $18.20  
  7 purchase totals = $874.73       $945.2402   $945.24   $945.25   $945.40