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	$209.45	10.236%	$230.8893	$230.89	$230.90	$230.90
Purchase #2	$103.33	5.243%	$108.7476	$108.75	$108.75	$108.70
Purchase #3	$88.39	12.684%	$99.6014	$99.60	$99.60	$99.60
Purchase #4	$64.89	3.625%	$67.2423	$67.24	$67.25	$67.20
Purchase #5	$42.88	8.258%	$46.421	$46.42	$46.40	$46.40
Purchase #6	$225.72	11.415%	$251.4859	$251.49	$251.50	$251.50
Purchase #7	$151.86	5.658%	$160.4522	$160.45	$160.45	$160.50
7 purchase totals =	$886.52		$964.8397	$964.84	$964.85	$964.80