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 $194.62   8.345%   $210.861   $210.86   $210.85   $210.90  
  Purchase #2 $106.86   8.732%   $116.191   $116.19   $116.20   $116.20  
  Purchase #3 $60.60   3.733%   $62.8622   $62.86   $62.85   $62.90  
  Purchase #4 $236.74   13.497%   $268.6928   $268.69   $268.70   $268.70  
  Purchase #5 $211.51   6.247%   $224.723   $224.72   $224.70   $224.70  
  Purchase #6 $26.96   6.482%   $28.7075   $28.71   $28.70   $28.70  
  Purchase #7 $177.55   9.269%   $194.0071   $194.01   $194.00   $194.00  
  7 purchase totals = $1,014.84       $1,106.0446   $1,106.04   $1,106.00   $1,106.10