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 $84.48   12.582%   $95.1093   $95.11   $95.10   $95.10  
  Purchase #2 $177.56   7.757%   $191.3333   $191.33   $191.35   $191.30  
  Purchase #3 $172.82   12.317%   $194.1062   $194.11   $194.10   $194.10  
  Purchase #4 $214.66   6.745%   $229.1388   $229.14   $229.15   $229.10  
  Purchase #5 $101.64   7.624%   $109.389   $109.39   $109.40   $109.40  
  Purchase #6 $159.57   9.678%   $175.0132   $175.01   $175.00   $175.00  
  Purchase #7 $208.73   8.327%   $226.1109   $226.11   $226.10   $226.10  
  7 purchase totals = $1,119.46       $1,220.2007   $1,220.20   $1,220.20   $1,220.10