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 $94.84   8.212%   $102.6283   $102.63   $102.65   $102.60  
  Purchase #2 $217.39   5.141%   $228.566   $228.57   $228.55   $228.60  
  Purchase #3 $215.69   8.311%   $233.616   $233.62   $233.60   $233.60  
  Purchase #4 $132.39   10.663%   $146.5067   $146.51   $146.50   $146.50  
  Purchase #5 $141.25   7.557%   $151.9243   $151.92   $151.90   $151.90  
  Purchase #6 $250.30   13.286%   $283.5549   $283.55   $283.55   $283.60  
  Purchase #7 $156.46   8.352%   $169.5275   $169.53   $169.55   $169.50  
  7 purchase totals = $1,208.32       $1,316.3237   $1,316.33   $1,316.30   $1,316.30