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 $82.73   12.370%   $92.9637   $92.96   $92.95   $93.00  
  Purchase #2 $236.44   12.285%   $265.4867   $265.49   $265.50   $265.50  
  Purchase #3 $164.59   5.726%   $174.0144   $174.01   $174.00   $174.00  
  Purchase #4 $219.66   7.325%   $235.7501   $235.75   $235.75   $235.80  
  Purchase #5 $177.56   13.310%   $201.1932   $201.19   $201.20   $201.20  
  Purchase #6 $120.76   10.307%   $133.2067   $133.21   $133.20   $133.20  
  Purchase #7 $243.79   6.355%   $259.2829   $259.28   $259.30   $259.30  
  7 purchase totals = $1,245.53       $1,361.8977   $1,361.89   $1,361.90   $1,362.00