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	$84.26	9.777%	$92.4981	$92.50	$92.50	$92.50
Purchase #2	$81.52	8.746%	$88.6497	$88.65	$88.65	$88.60
Purchase #3	$48.65	3.569%	$50.3863	$50.39	$50.40	$50.40
Purchase #4	$171.31	13.570%	$194.5568	$194.56	$194.55	$194.60
Purchase #5	$158.85	4.190%	$165.5058	$165.51	$165.50	$165.50
Purchase #6	$79.46	12.300%	$89.2336	$89.23	$89.25	$89.20
Purchase #7	$55.91	12.252%	$62.7601	$62.76	$62.75	$62.80
7 purchase totals =	$679.96		$743.5904	$743.60	$743.60	$743.60