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 $46.86   5.559%   $49.4649   $49.46   $49.45   $49.50  
  Purchase #2 $229.86   11.456%   $256.1928   $256.19   $256.20   $256.20  
  Purchase #3 $214.86   4.132%   $223.738   $223.74   $223.75   $223.70  
  Purchase #4 $69.79   6.170%   $74.096   $74.10   $74.10   $74.10  
  Purchase #5 $236.88   3.808%   $245.9004   $245.90   $245.90   $245.90  
  Purchase #6 $209.65   6.480%   $223.2353   $223.24   $223.25   $223.20  
  Purchase #7 $107.56   7.465%   $115.5894   $115.59   $115.60   $115.60  
  7 purchase totals = $1,115.46       $1,188.2168   $1,188.22   $1,188.25   $1,188.20