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	$174.48	5.754%	$184.5196	$184.52	$184.50	$184.50
Purchase #2	$106.89	12.388%	$120.1315	$120.13	$120.15	$120.10
Purchase #3	$116.83	10.773%	$129.4161	$129.42	$129.40	$129.40
Purchase #4	$33.46	13.288%	$37.9062	$37.91	$37.90	$37.90
Purchase #5	$140.87	12.364%	$158.2872	$158.29	$158.30	$158.30
Purchase #6	$223.72	13.535%	$254.0005	$254.00	$254.00	$254.00
Purchase #7	$142.55	12.658%	$160.594	$160.59	$160.60	$160.60
7 purchase totals =	$938.80		$1,044.8551	$1,044.86	$1,044.85	$1,044.80