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	$194.66	11.399%	$216.8493	$216.85	$216.85	$216.80
Purchase #2	$44.27	13.538%	$50.2633	$50.26	$50.25	$50.30
Purchase #3	$101.73	8.550%	$110.4279	$110.43	$110.45	$110.40
Purchase #4	$114.65	11.186%	$127.4747	$127.47	$127.45	$127.50
Purchase #5	$186.62	9.869%	$205.0375	$205.04	$205.05	$205.00
Purchase #6	$57.28	4.616%	$59.924	$59.92	$59.90	$59.90
Purchase #7	$47.89	12.439%	$53.847	$53.85	$53.85	$53.80
7 purchase totals =	$747.10		$823.8237	$823.82	$823.80	$823.70