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 $216.43   13.130%   $244.8473   $244.85   $244.85   $244.80  
  Purchase #2 $91.53   4.219%   $95.3917   $95.39   $95.40   $95.40  
  Purchase #3 $31.84   11.636%   $35.5449   $35.54   $35.55   $35.50  
  Purchase #4 $168.40   11.213%   $187.2827   $187.28   $187.30   $187.30  
  Purchase #5 $148.47   4.525%   $155.1883   $155.19   $155.20   $155.20  
  Purchase #6 $158.53   13.335%   $179.67   $179.67   $179.65   $179.70  
  Purchase #7 $140.82   4.425%   $147.0513   $147.05   $147.05   $147.10  
  7 purchase totals = $956.02       $1,044.9762   $1,044.97   $1,045.00   $1,045.00