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	$184.83	3.764%	$191.787	$191.79	$191.80	$191.80
Purchase #2	$38.55	11.267%	$42.8934	$42.89	$42.90	$42.90
Purchase #3	$150.85	7.419%	$162.0416	$162.04	$162.05	$162.00
Purchase #4	$245.30	4.105%	$255.3696	$255.37	$255.35	$255.40
Purchase #5	$203.77	9.778%	$223.6946	$223.69	$223.70	$223.70
Purchase #6	$70.44	6.858%	$75.2708	$75.27	$75.25	$75.30
Purchase #7	$90.66	5.381%	$95.5384	$95.54	$95.55	$95.50
7 purchase totals =	$984.40		$1,046.5954	$1,046.59	$1,046.60	$1,046.60