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 $194.96   3.464%   $201.7134   $201.71   $201.70   $201.70  
  Purchase #2 $98.31   6.131%   $104.3374   $104.34   $104.35   $104.30  
  Purchase #3 $229.60   6.399%   $244.2921   $244.29   $244.30   $244.30  
  Purchase #4 $198.55   5.598%   $209.6648   $209.66   $209.65   $209.70  
  Purchase #5 $108.28   6.467%   $115.2825   $115.28   $115.30   $115.30  
  Purchase #6 $167.64   3.308%   $173.1855   $173.19   $173.20   $173.20  
  Purchase #7 $200.48   11.707%   $223.9502   $223.95   $223.95   $224.00  
  7 purchase totals = $1,197.82       $1,272.4259   $1,272.42   $1,272.45   $1,272.50