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 $43.44   5.769%   $45.9461   $45.95   $45.95   $45.90  
  Purchase #2 $92.35   4.413%   $96.4254   $96.43   $96.45   $96.40  
  Purchase #3 $45.62   10.672%   $50.4886   $50.49   $50.50   $50.50  
  Purchase #4 $187.96   5.457%   $198.217   $198.22   $198.20   $198.20  
  Purchase #5 $63.85   8.414%   $69.2223   $69.22   $69.20   $69.20  
  Purchase #6 $122.36   8.135%   $132.314   $132.31   $132.30   $132.30  
  Purchase #7 $202.43   6.285%   $215.1527   $215.15   $215.15   $215.20  
  7 purchase totals = $758.01       $807.7661   $807.77   $807.75   $807.70