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	$177.34	8.102%	$191.7081	$191.71	$191.70	$191.70
Purchase #2	$111.42	13.552%	$126.5196	$126.52	$126.50	$126.50
Purchase #3	$32.43	4.131%	$33.7697	$33.77	$33.75	$33.80
Purchase #4	$170.36	9.487%	$186.5221	$186.52	$186.50	$186.50
Purchase #5	$101.38	9.140%	$110.6461	$110.65	$110.65	$110.60
Purchase #6	$135.78	7.141%	$145.476	$145.48	$145.50	$145.50
Purchase #7	$53.78	13.536%	$61.0597	$61.06	$61.05	$61.10
7 purchase totals =	$782.49		$855.7013	$855.71	$855.65	$855.70