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 $217.84   12.364%   $244.7737   $244.77   $244.75   $244.80  
  Purchase #2 $196.61   9.509%   $215.3056   $215.31   $215.30   $215.30  
  Purchase #3 $22.84   9.364%   $24.9787   $24.98   $25.00   $25.00  
  Purchase #4 $242.80   10.802%   $269.0273   $269.03   $269.05   $269.00  
  Purchase #5 $223.75   12.314%   $251.3026   $251.30   $251.30   $251.30  
  Purchase #6 $97.50   11.546%   $108.7574   $108.76   $108.75   $108.80  
  Purchase #7 $138.27   9.401%   $151.2688   $151.27   $151.25   $151.30  
  7 purchase totals = $1,139.61       $1,265.4141   $1,265.42   $1,265.40   $1,265.50