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	$175.28	8.710%	$190.5469	$190.55	$190.55	$190.50
Purchase #2	$74.69	4.605%	$78.1295	$78.13	$78.15	$78.10
Purchase #3	$99.46	5.103%	$104.5354	$104.54	$104.55	$104.50
Purchase #4	$197.50	11.829%	$220.8623	$220.86	$220.85	$220.90
Purchase #5	$22.59	13.681%	$25.6805	$25.68	$25.70	$25.70
Purchase #6	$58.56	7.523%	$62.9655	$62.97	$62.95	$63.00
Purchase #7	$55.77	6.729%	$59.5228	$59.52	$59.50	$59.50
7 purchase totals =	$683.85		$742.2429	$742.25	$742.25	$742.20