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 $93.97   11.418%   $104.6995   $104.70   $104.70   $104.70  
  Purchase #2 $88.41   6.377%   $94.0479   $94.05   $94.05   $94.00  
  Purchase #3 $201.43   8.868%   $219.2928   $219.29   $219.30   $219.30  
  Purchase #4 $84.69   13.703%   $96.2951   $96.30   $96.30   $96.30  
  Purchase #5 $182.33   12.533%   $205.1814   $205.18   $205.20   $205.20  
  Purchase #6 $188.42   7.684%   $202.8982   $202.90   $202.90   $202.90  
  Purchase #7 $96.58   4.588%   $101.0111   $101.01   $101.00   $101.00  
  7 purchase totals = $935.83       $1,023.4260   $1,023.43   $1,023.45   $1,023.40