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 $195.36   9.521%   $213.9602   $213.96   $213.95   $214.00  
  Purchase #2 $97.59   4.585%   $102.0645   $102.06   $102.05   $102.10  
  Purchase #3 $205.96   12.163%   $231.0109   $231.01   $231.00   $231.00  
  Purchase #4 $248.78   5.504%   $262.4729   $262.47   $262.45   $262.50  
  Purchase #5 $217.66   13.656%   $247.3836   $247.38   $247.40   $247.40  
  Purchase #6 $116.79   9.861%   $128.3067   $128.31   $128.30   $128.30  
  Purchase #7 $172.39   9.511%   $188.786   $188.79   $188.80   $188.80  
  7 purchase totals = $1,254.53       $1,373.9848   $1,373.98   $1,373.95   $1,374.10