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	$55.30	6.864%	$59.0958	$59.10	$59.10	$59.10
Purchase #2	$237.88	5.502%	$250.9682	$250.97	$250.95	$251.00
Purchase #3	$9.50	11.739%	$10.6152	$10.62	$10.60	$10.60
Purchase #4	$149.87	5.713%	$158.4321	$158.43	$158.45	$158.40
Purchase #5	$67.82	4.507%	$70.8766	$70.88	$70.90	$70.90
Purchase #6	$228.34	4.465%	$238.5354	$238.54	$238.55	$238.50
Purchase #7	$150.25	5.672%	$158.7722	$158.77	$158.75	$158.80
7 purchase totals =	$898.96		$947.2955	$947.31	$947.30	$947.30