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	$243.39	10.822%	$269.7297	$269.73	$269.75	$269.70
Purchase #2	$74.52	3.325%	$76.9978	$77.00	$77.00	$77.00
Purchase #3	$85.67	4.610%	$89.6194	$89.62	$89.60	$89.60
Purchase #4	$41.80	13.796%	$47.5667	$47.57	$47.55	$47.60
Purchase #5	$91.67	8.769%	$99.7085	$99.71	$99.70	$99.70
Purchase #6	$41.57	10.610%	$45.9806	$45.98	$46.00	$46.00
Purchase #7	$134.55	13.376%	$152.5474	$152.55	$152.55	$152.50
7 purchase totals =	$713.17		$782.1501	$782.16	$782.15	$782.10