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 $219.40   12.568%   $246.9742   $246.97   $246.95   $247.00  
  Purchase #2 $248.98   10.599%   $275.3694   $275.37   $275.35   $275.40  
  Purchase #3 $214.37   10.724%   $237.359   $237.36   $237.35   $237.40  
  Purchase #4 $216.71   11.290%   $241.1766   $241.18   $241.20   $241.20  
  Purchase #5 $160.59   4.375%   $167.6158   $167.62   $167.60   $167.60  
  Purchase #6 $197.54   5.201%   $207.8141   $207.81   $207.80   $207.80  
  Purchase #7 $78.77   13.223%   $89.1858   $89.19   $89.20   $89.20  
  7 purchase totals = $1,336.36       $1,465.4949   $1,465.50   $1,465.45   $1,465.60