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 $46.85   5.818%   $49.5757   $49.58   $49.60   $49.60  
  Purchase #2 $194.65   4.653%   $203.7071   $203.71   $203.70   $203.70  
  Purchase #3 $48.70   9.427%   $53.2909   $53.29   $53.30   $53.30  
  Purchase #4 $70.68   3.399%   $73.0824   $73.08   $73.10   $73.10  
  Purchase #5 $247.42   7.507%   $265.9938   $265.99   $266.00   $266.00  
  Purchase #6 $139.62   8.207%   $151.0786   $151.08   $151.10   $151.10  
  Purchase #7 $69.25   5.393%   $72.9847   $72.98   $73.00   $73.00  
  7 purchase totals = $817.17       $869.7132   $869.71   $869.80   $869.80