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	$158.81	9.325%	$173.619	$173.62	$173.60	$173.60
Purchase #2	$57.38	4.222%	$59.8026	$59.80	$59.80	$59.80
Purchase #3	$95.58	5.339%	$100.683	$100.68	$100.70	$100.70
Purchase #4	$118.39	9.364%	$129.476	$129.48	$129.50	$129.50
Purchase #5	$25.88	9.338%	$28.2967	$28.30	$28.30	$28.30
Purchase #6	$82.66	10.480%	$91.3228	$91.32	$91.30	$91.30
Purchase #7	$202.50	10.506%	$223.7747	$223.77	$223.75	$223.80
7 purchase totals =	$741.20		$806.9748	$806.97	$806.95	$807.00