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 $84.30   4.331%   $87.951   $87.95   $87.95   $88.00  
  Purchase #2 $112.49   5.359%   $118.5183   $118.52   $118.50   $118.50  
  Purchase #3 $73.94   3.651%   $76.6395   $76.64   $76.65   $76.60  
  Purchase #4 $116.38   3.869%   $120.8827   $120.88   $120.90   $120.90  
  Purchase #5 $178.47   7.102%   $191.1449   $191.14   $191.15   $191.10  
  Purchase #6 $232.39   5.299%   $244.7043   $244.70   $244.70   $244.70  
  Purchase #7 $166.75   10.507%   $184.2704   $184.27   $184.25   $184.30  
  7 purchase totals = $964.72       $1,024.1111   $1,024.10   $1,024.10   $1,024.10