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 $213.76   10.763%   $236.767   $236.77   $236.75   $236.80  
  Purchase #2 $11.34   7.167%   $12.1527   $12.15   $12.15   $12.20  
  Purchase #3 $234.65   4.560%   $245.35   $245.35   $245.35   $245.40  
  Purchase #4 $218.79   11.542%   $244.0427   $244.04   $244.05   $244.00  
  Purchase #5 $104.68   6.431%   $111.412   $111.41   $111.40   $111.40  
  Purchase #6 $227.63   10.316%   $251.1123   $251.11   $251.10   $251.10  
  Purchase #7 $5.59   12.299%   $6.2775   $6.28   $6.30   $6.30  
  7 purchase totals = $1,016.44       $1,107.1142   $1,107.11   $1,107.10   $1,107.20