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 $116.42   5.610%   $122.9512   $122.95   $122.95   $123.00  
  Purchase #2 $109.38   8.207%   $118.3568   $118.36   $118.35   $118.40  
  Purchase #3 $167.29   10.223%   $184.3921   $184.39   $184.40   $184.40  
  Purchase #4 $51.28   6.787%   $54.7604   $54.76   $54.75   $54.80  
  Purchase #5 $41.35   6.549%   $44.058   $44.06   $44.05   $44.10  
  Purchase #6 $167.36   4.483%   $174.8627   $174.86   $174.85   $174.90  
  Purchase #7 $58.99   10.827%   $65.3768   $65.38   $65.40   $65.40  
  7 purchase totals = $712.07       $764.7580   $764.76   $764.75   $765.00