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	$160.51	3.243%	$165.7153	$165.72	$165.70	$165.70
Purchase #2	$49.62	13.756%	$56.4457	$56.45	$56.45	$56.40
Purchase #3	$16.41	8.831%	$17.8592	$17.86	$17.85	$17.90
Purchase #4	$235.61	7.859%	$254.1266	$254.13	$254.15	$254.10
Purchase #5	$179.78	7.507%	$193.2761	$193.28	$193.30	$193.30
Purchase #6	$155.51	10.536%	$171.8945	$171.89	$171.90	$171.90
Purchase #7	$154.59	13.566%	$175.5617	$175.56	$175.55	$175.60
7 purchase totals =	$952.03		$1,034.8791	$1,034.89	$1,034.90	$1,034.90