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 $196.77   5.461%   $207.5156   $207.52   $207.50   $207.50  
  Purchase #2 $187.27   5.346%   $197.2815   $197.28   $197.30   $197.30  
  Purchase #3 $33.78   11.305%   $37.5988   $37.60   $37.60   $37.60  
  Purchase #4 $7.26   8.749%   $7.8952   $7.90   $7.90   $7.90  
  Purchase #5 $187.44   10.414%   $206.96   $206.96   $206.95   $207.00  
  Purchase #6 $59.38   4.253%   $61.9054   $61.91   $61.90   $61.90  
  Purchase #7 $58.34   11.831%   $65.2422   $65.24   $65.25   $65.20  
  7 purchase totals = $730.24       $784.3987   $784.41   $784.40   $784.40