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	$201.68	3.777%	$209.2975	$209.30	$209.30	$209.30
Purchase #2	$155.62	6.481%	$165.7057	$165.71	$165.70	$165.70
Purchase #3	$54.26	9.717%	$59.5324	$59.53	$59.55	$59.50
Purchase #4	$54.71	8.211%	$59.2022	$59.20	$59.20	$59.20
Purchase #5	$54.74	13.415%	$62.0834	$62.08	$62.10	$62.10
Purchase #6	$206.27	5.806%	$218.246	$218.25	$218.25	$218.20
Purchase #7	$47.76	9.639%	$52.3636	$52.36	$52.35	$52.40
7 purchase totals =	$775.04		$826.4308	$826.43	$826.45	$826.40