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	$248.62	8.279%	$269.2032	$269.20	$269.20	$269.20
Purchase #2	$40.89	3.739%	$42.4189	$42.42	$42.40	$42.40
Purchase #3	$38.73	12.308%	$43.4969	$43.50	$43.50	$43.50
Purchase #4	$153.41	3.291%	$158.4587	$158.46	$158.45	$158.50
Purchase #5	$104.63	8.821%	$113.8594	$113.86	$113.85	$113.90
Purchase #6	$95.83	10.810%	$106.1892	$106.19	$106.20	$106.20
Purchase #7	$238.90	9.847%	$262.4245	$262.42	$262.40	$262.40
7 purchase totals =	$921.01		$996.0508	$996.05	$996.00	$996.10