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	$20.99	5.510%	$22.1465	$22.15	$22.15	$22.10
Purchase #2	$138.55	9.545%	$151.7746	$151.77	$151.75	$151.80
Purchase #3	$164.88	9.689%	$180.8552	$180.86	$180.85	$180.90
Purchase #4	$159.91	7.845%	$172.4549	$172.45	$172.45	$172.50
Purchase #5	$45.76	3.682%	$47.4449	$47.44	$47.45	$47.40
Purchase #6	$214.83	13.825%	$244.5302	$244.53	$244.55	$244.50
Purchase #7	$233.66	4.645%	$244.5135	$244.51	$244.50	$244.50
7 purchase totals =	$978.58		$1,063.7198	$1,063.71	$1,063.70	$1,063.70