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	$117.93	10.623%	$130.4577	$130.46	$130.45	$130.50
Purchase #2	$149.45	13.673%	$169.8843	$169.88	$169.90	$169.90
Purchase #3	$242.45	13.714%	$275.6996	$275.70	$275.70	$275.70
Purchase #4	$105.57	12.349%	$118.6068	$118.61	$118.60	$118.60
Purchase #5	$232.33	9.593%	$254.6174	$254.62	$254.60	$254.60
Purchase #6	$180.73	5.305%	$190.3177	$190.32	$190.30	$190.30
Purchase #7	$17.44	6.463%	$18.5671	$18.57	$18.55	$18.60
7 purchase totals =	$1,045.90		$1,158.1506	$1,158.16	$1,158.10	$1,158.20