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 $69.83   8.785%   $75.9646   $75.96   $75.95   $76.00  
  Purchase #2 $237.57   10.590%   $262.7287   $262.73   $262.75   $262.70  
  Purchase #3 $91.67   3.641%   $95.0077   $95.01   $95.00   $95.00  
  Purchase #4 $206.26   3.642%   $213.772   $213.77   $213.75   $213.80  
  Purchase #5 $99.97   6.746%   $106.714   $106.71   $106.70   $106.70  
  Purchase #6 $211.85   12.780%   $238.9244   $238.92   $238.90   $238.90  
  Purchase #7 $46.32   12.375%   $52.0521   $52.05   $52.05   $52.10  
  7 purchase totals = $963.47       $1,045.1635   $1,045.15   $1,045.10   $1,045.20