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 $86.30   11.764%   $96.4523   $96.45   $96.45   $96.50  
  Purchase #2 $137.56   5.389%   $144.9731   $144.97   $144.95   $145.00  
  Purchase #3 $178.73   8.238%   $193.4538   $193.45   $193.45   $193.50  
  Purchase #4 $220.53   10.554%   $243.8047   $243.80   $243.80   $243.80  
  Purchase #5 $208.43   13.384%   $236.3263   $236.33   $236.35   $236.30  
  Purchase #6 $230.69   8.644%   $250.6308   $250.63   $250.65   $250.60  
  Purchase #7 $223.64   10.172%   $246.3887   $246.39   $246.40   $246.40  
  7 purchase totals = $1,285.88       $1,412.0297   $1,412.02   $1,412.05   $1,412.10