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	$49.68	7.614%	$53.4626	$53.46	$53.45	$53.50
Purchase #2	$145.27	10.521%	$160.5539	$160.55	$160.55	$160.60
Purchase #3	$165.52	4.353%	$172.7251	$172.73	$172.75	$172.70
Purchase #4	$242.76	7.237%	$260.3285	$260.33	$260.35	$260.30
Purchase #5	$56.27	6.239%	$59.7807	$59.78	$59.80	$59.80
Purchase #6	$102.29	5.575%	$107.9927	$107.99	$108.00	$108.00
Purchase #7	$214.72	13.767%	$244.2805	$244.28	$244.30	$244.30
7 purchase totals =	$976.51		$1,059.1240	$1,059.12	$1,059.20	$1,059.20