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 $178.63   9.154%   $194.9818   $194.98   $195.00   $195.00  
  Purchase #2 $87.97   10.777%   $97.4505   $97.45   $97.45   $97.50  
  Purchase #3 $161.53   6.427%   $171.9115   $171.91   $171.90   $171.90  
  Purchase #4 $54.91   4.773%   $57.5309   $57.53   $57.55   $57.50  
  Purchase #5 $99.30   7.400%   $106.6482   $106.65   $106.65   $106.60  
  Purchase #6 $131.96   8.767%   $143.5289   $143.53   $143.55   $143.50  
  Purchase #7 $236.46   7.284%   $253.6837   $253.68   $253.70   $253.70  
  7 purchase totals = $950.76       $1,025.7355   $1,025.73   $1,025.80   $1,025.70