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 $86.96   6.481%   $92.5959   $92.60   $92.60   $92.60  
  Purchase #2 $234.75   4.795%   $246.0063   $246.01   $246.00   $246.00  
  Purchase #3 $213.53   7.509%   $229.564   $229.56   $229.55   $229.60  
  Purchase #4 $161.56   3.648%   $167.4537   $167.45   $167.45   $167.50  
  Purchase #5 $158.65   8.833%   $172.6636   $172.66   $172.65   $172.70  
  Purchase #6 $90.84   7.288%   $97.4604   $97.46   $97.45   $97.50  
  Purchase #7 $199.55   3.674%   $206.8815   $206.88   $206.90   $206.90  
  7 purchase totals = $1,145.84       $1,212.6254   $1,212.62   $1,212.60   $1,212.80