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 $185.68   6.272%   $197.3258   $197.33   $197.35   $197.30  
  Purchase #2 $97.67   6.562%   $104.0791   $104.08   $104.10   $104.10  
  Purchase #3 $244.28   6.275%   $259.6086   $259.61   $259.60   $259.60  
  Purchase #4 $229.35   6.326%   $243.8587   $243.86   $243.85   $243.90  
  Purchase #5 $196.87   8.380%   $213.3677   $213.37   $213.35   $213.40  
  Purchase #6 $96.76   6.373%   $102.9265   $102.93   $102.95   $102.90  
  Purchase #7 $81.38   5.480%   $85.8396   $85.84   $85.85   $85.80  
  7 purchase totals = $1,131.99       $1,207.0060   $1,207.02   $1,207.05   $1,207.00