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	$109.27	12.181%	$122.5802	$122.58	$122.60	$122.60
Purchase #2	$205.48	13.772%	$233.7787	$233.78	$233.80	$233.80
Purchase #3	$200.87	5.700%	$212.3196	$212.32	$212.30	$212.30
Purchase #4	$46.57	5.837%	$49.2883	$49.29	$49.30	$49.30
Purchase #5	$131.25	10.340%	$144.8213	$144.82	$144.80	$144.80
Purchase #6	$216.60	4.574%	$226.5073	$226.51	$226.50	$226.50
Purchase #7	$124.41	5.325%	$131.0348	$131.03	$131.05	$131.00
7 purchase totals =	$1,034.45		$1,120.3302	$1,120.33	$1,120.35	$1,120.30