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 $62.43   7.650%   $67.2059   $67.21   $67.20   $67.20  
  Purchase #2 $76.37   3.431%   $78.9903   $78.99   $79.00   $79.00  
  Purchase #3 $116.85   3.377%   $120.796   $120.80   $120.80   $120.80  
  Purchase #4 $204.85   6.330%   $217.817   $217.82   $217.80   $217.80  
  Purchase #5 $232.74   5.738%   $246.0946   $246.09   $246.10   $246.10  
  Purchase #6 $73.35   4.792%   $76.8649   $76.86   $76.85   $76.90  
  Purchase #7 $217.51   12.514%   $244.7292   $244.73   $244.75   $244.70  
  7 purchase totals = $984.10       $1,052.4979   $1,052.50   $1,052.50   $1,052.50