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 $204.73   4.663%   $214.2766   $214.28   $214.30   $214.30  
  Purchase #2 $11.84   10.602%   $13.0953   $13.10   $13.10   $13.10  
  Purchase #3 $45.65   6.465%   $48.6013   $48.60   $48.60   $48.60  
  Purchase #4 $189.83   9.251%   $207.3912   $207.39   $207.40   $207.40  
  Purchase #5 $93.43   8.763%   $101.6173   $101.62   $101.60   $101.60  
  Purchase #6 $57.85   3.701%   $59.991   $59.99   $60.00   $60.00  
  Purchase #7 $88.60   13.373%   $100.4485   $100.45   $100.45   $100.40  
  7 purchase totals = $691.93       $745.4212   $745.43   $745.45   $745.40