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 $41.63   5.730%   $44.0154   $44.02   $44.00   $44.00  
  Purchase #2 $217.86   4.131%   $226.8598   $226.86   $226.85   $226.90  
  Purchase #3 $140.96   4.716%   $147.6077   $147.61   $147.60   $147.60  
  Purchase #4 $101.96   13.387%   $115.6094   $115.61   $115.60   $115.60  
  Purchase #5 $228.71   11.551%   $255.1283   $255.13   $255.15   $255.10  
  Purchase #6 $184.64   5.569%   $194.9226   $194.92   $194.90   $194.90  
  Purchase #7 $122.98   6.114%   $130.499   $130.50   $130.50   $130.50  
  7 purchase totals = $1,038.74       $1,114.6422   $1,114.65   $1,114.60   $1,114.60