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 $244.60   9.242%   $267.2059   $267.21   $267.20   $267.20  
  Purchase #2 $211.69   13.343%   $239.9358   $239.94   $239.95   $239.90  
  Purchase #3 $156.43   8.478%   $169.6921   $169.69   $169.70   $169.70  
  Purchase #4 $164.47   12.621%   $185.2278   $185.23   $185.25   $185.20  
  Purchase #5 $194.64   5.635%   $205.608   $205.61   $205.60   $205.60  
  Purchase #6 $181.33   13.266%   $205.3852   $205.39   $205.40   $205.40  
  Purchase #7 $197.44   8.629%   $214.4771   $214.48   $214.50   $214.50  
  7 purchase totals = $1,350.60       $1,487.5319   $1,487.55   $1,487.60   $1,487.50