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	$59.43	12.236%	$66.7019	$66.70	$66.70	$66.70
Purchase #2	$29.62	13.524%	$33.6258	$33.63	$33.65	$33.60
Purchase #3	$89.30	3.814%	$92.7059	$92.71	$92.70	$92.70
Purchase #4	$72.81	7.629%	$78.3647	$78.36	$78.35	$78.40
Purchase #5	$78.30	5.666%	$82.7365	$82.74	$82.75	$82.70
Purchase #6	$134.26	13.643%	$152.5771	$152.58	$152.60	$152.60
Purchase #7	$53.55	4.390%	$55.9008	$55.90	$55.90	$55.90
7 purchase totals =	$517.27		$562.6127	$562.62	$562.65	$562.60