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 $84.69   12.263%   $95.0755   $95.08   $95.10   $95.10  
  Purchase #2 $61.67   8.123%   $66.6795   $66.68   $66.70   $66.70  
  Purchase #3 $109.83   12.852%   $123.9454   $123.95   $123.95   $123.90  
  Purchase #4 $172.86   11.785%   $193.2316   $193.23   $193.25   $193.20  
  Purchase #5 $204.67   12.663%   $230.5874   $230.59   $230.60   $230.60  
  Purchase #6 $94.73   9.468%   $103.699   $103.70   $103.70   $103.70  
  Purchase #7 $138.62   8.661%   $150.6259   $150.63   $150.65   $150.60  
  7 purchase totals = $867.07       $963.8443   $963.86   $963.95   $963.80