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	$212.78	4.864%	$223.1296	$223.13	$223.15	$223.10
Purchase #2	$122.42	13.783%	$139.2931	$139.29	$139.30	$139.30
Purchase #3	$105.44	12.621%	$118.7476	$118.75	$118.75	$118.70
Purchase #4	$235.30	13.518%	$267.1079	$267.11	$267.10	$267.10
Purchase #5	$135.27	9.625%	$148.2897	$148.29	$148.30	$148.30
Purchase #6	$150.63	5.712%	$159.234	$159.23	$159.25	$159.20
Purchase #7	$85.70	5.768%	$90.6432	$90.64	$90.65	$90.60
7 purchase totals =	$1,047.54		$1,146.4451	$1,146.44	$1,146.50	$1,146.30