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 $213.42   9.110%   $232.8626   $232.86   $232.85   $232.90  
  Purchase #2 $196.39   11.480%   $218.9356   $218.94   $218.95   $218.90  
  Purchase #3 $91.93   11.424%   $102.4321   $102.43   $102.45   $102.40  
  Purchase #4 $194.31   9.591%   $212.9463   $212.95   $212.95   $212.90  
  Purchase #5 $188.95   9.342%   $206.6017   $206.60   $206.60   $206.60  
  Purchase #6 $95.86   11.548%   $106.9299   $106.93   $106.95   $106.90  
  Purchase #7 $249.34   9.784%   $273.7354   $273.74   $273.75   $273.70  
  7 purchase totals = $1,230.20       $1,354.4436   $1,354.45   $1,354.50   $1,354.30