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	$72.33	13.729%	$82.2602	$82.26	$82.25	$82.30
Purchase #2	$29.38	9.344%	$32.1253	$32.13	$32.15	$32.10
Purchase #3	$56.42	5.719%	$59.6467	$59.65	$59.65	$59.60
Purchase #4	$158.42	4.698%	$165.8626	$165.86	$165.85	$165.90
Purchase #5	$56.86	3.189%	$58.6733	$58.67	$58.65	$58.70
Purchase #6	$104.88	5.366%	$110.5079	$110.51	$110.50	$110.50
Purchase #7	$30.25	11.205%	$33.6395	$33.64	$33.65	$33.60
7 purchase totals =	$508.54		$542.7155	$542.72	$542.70	$542.70