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 $69.37   7.673%   $74.6928   $74.69   $74.70   $74.70  
  Purchase #2 $92.43   13.697%   $105.0901   $105.09   $105.10   $105.10  
  Purchase #3 $99.98   13.772%   $113.7492   $113.75   $113.75   $113.70  
  Purchase #4 $206.51   9.473%   $226.0727   $226.07   $226.05   $226.10  
  Purchase #5 $119.30   6.327%   $126.8481   $126.85   $126.85   $126.80  
  Purchase #6 $143.28   4.590%   $149.8566   $149.86   $149.85   $149.90  
  Purchase #7 $151.77   4.157%   $158.0791   $158.08   $158.10   $158.10  
  7 purchase totals = $882.64       $954.3886   $954.39   $954.40   $954.40