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	$145.76	12.861%	$164.5062	$164.51	$164.50	$164.50
Purchase #2	$146.77	7.227%	$157.3771	$157.38	$157.40	$157.40
Purchase #3	$247.97	7.425%	$266.3818	$266.38	$266.40	$266.40
Purchase #4	$48.33	8.787%	$52.5768	$52.58	$52.60	$52.60
Purchase #5	$171.78	11.457%	$191.4608	$191.46	$191.45	$191.50
Purchase #6	$175.37	11.456%	$195.4604	$195.46	$195.45	$195.50
Purchase #7	$124.43	5.508%	$131.2836	$131.28	$131.30	$131.30
7 purchase totals =	$1,060.41		$1,159.0467	$1,159.05	$1,159.10	$1,159.20