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 $204.39   9.467%   $223.7396   $223.74   $223.75   $223.70  
  Purchase #2 $215.65   9.869%   $236.9325   $236.93   $236.95   $236.90  
  Purchase #3 $41.50   4.346%   $43.3036   $43.30   $43.30   $43.30  
  Purchase #4 $198.87   4.743%   $208.3024   $208.30   $208.30   $208.30  
  Purchase #5 $88.42   4.213%   $92.1451   $92.15   $92.15   $92.10  
  Purchase #6 $189.68   8.714%   $206.2087   $206.21   $206.20   $206.20  
  Purchase #7 $106.68   5.763%   $112.828   $112.83   $112.85   $112.80  
  7 purchase totals = $1,045.19       $1,123.4599   $1,123.46   $1,123.50   $1,123.30