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 $214.35   10.662%   $237.204   $237.20   $237.20   $237.20  
  Purchase #2 $205.36   9.497%   $224.863   $224.86   $224.85   $224.90  
  Purchase #3 $177.29   10.398%   $195.7246   $195.72   $195.70   $195.70  
  Purchase #4 $181.97   7.628%   $195.8507   $195.85   $195.85   $195.90  
  Purchase #5 $236.98   13.114%   $268.0576   $268.06   $268.05   $268.10  
  Purchase #6 $162.37   8.517%   $176.1991   $176.20   $176.20   $176.20  
  Purchase #7 $42.87   12.470%   $48.2159   $48.22   $48.20   $48.20  
  7 purchase totals = $1,221.19       $1,346.1149   $1,346.11   $1,346.05   $1,346.20