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 $115.27   9.288%   $125.9763   $125.98   $126.00   $126.00  
  Purchase #2 $217.62   12.869%   $245.6255   $245.63   $245.65   $245.60  
  Purchase #3 $147.52   4.394%   $154.002   $154.00   $154.00   $154.00  
  Purchase #4 $53.55   13.132%   $60.5822   $60.58   $60.60   $60.60  
  Purchase #5 $159.87   5.629%   $168.8691   $168.87   $168.85   $168.90  
  Purchase #6 $88.35   6.866%   $94.4161   $94.42   $94.40   $94.40  
  Purchase #7 $237.56   4.468%   $248.1742   $248.17   $248.15   $248.20  
  7 purchase totals = $1,019.74       $1,097.6454   $1,097.65   $1,097.65   $1,097.70