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 $58.33   6.214%   $61.9546   $61.95   $61.95   $62.00  
  Purchase #2 $209.84   9.472%   $229.716   $229.72   $229.70   $229.70  
  Purchase #3 $26.68   5.230%   $28.0754   $28.08   $28.10   $28.10  
  Purchase #4 $141.48   8.742%   $153.8482   $153.85   $153.85   $153.80  
  Purchase #5 $188.96   3.367%   $195.3223   $195.32   $195.30   $195.30  
  Purchase #6 $87.96   10.744%   $97.4104   $97.41   $97.40   $97.40  
  Purchase #7 $43.36   10.506%   $47.9154   $47.92   $47.90   $47.90  
  7 purchase totals = $756.61       $814.2423   $814.25   $814.20   $814.20