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 $84.37   13.188%   $95.4967   $95.50   $95.50   $95.50  
  Purchase #2 $170.26   12.433%   $191.4284   $191.43   $191.45   $191.40  
  Purchase #3 $65.63   3.527%   $67.9448   $67.94   $67.95   $67.90  
  Purchase #4 $165.86   6.367%   $176.4203   $176.42   $176.40   $176.40  
  Purchase #5 $238.80   4.540%   $249.6415   $249.64   $249.65   $249.60  
  Purchase #6 $22.27   12.340%   $25.0181   $25.02   $25.00   $25.00  
  Purchase #7 $215.40   4.225%   $224.5007   $224.50   $224.50   $224.50  
  7 purchase totals = $962.59       $1,030.4505   $1,030.45   $1,030.45   $1,030.30