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	$87.62	4.340%	$91.4227	$91.42	$91.40	$91.40
Purchase #2	$95.68	3.526%	$99.0537	$99.05	$99.05	$99.10
Purchase #3	$89.39	6.801%	$95.4694	$95.47	$95.45	$95.50
Purchase #4	$35.35	5.800%	$37.4003	$37.40	$37.40	$37.40
Purchase #5	$193.40	3.714%	$200.5829	$200.58	$200.60	$200.60
Purchase #6	$154.49	7.247%	$165.6859	$165.69	$165.70	$165.70
Purchase #7	$145.94	13.546%	$165.709	$165.71	$165.70	$165.70
7 purchase totals =	$801.87		$855.3239	$855.32	$855.30	$855.40