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	$173.71	7.803%	$187.2646	$187.26	$187.25	$187.30
Purchase #2	$48.72	7.742%	$52.4919	$52.49	$52.50	$52.50
Purchase #3	$154.43	11.198%	$171.7231	$171.72	$171.70	$171.70
Purchase #4	$236.70	5.368%	$249.4061	$249.41	$249.40	$249.40
Purchase #5	$156.86	13.584%	$178.1679	$178.17	$178.15	$178.20
Purchase #6	$142.77	11.412%	$159.0629	$159.06	$159.05	$159.10
Purchase #7	$242.91	5.269%	$255.7089	$255.71	$255.70	$255.70
7 purchase totals =	$1,156.10		$1,253.8254	$1,253.82	$1,253.75	$1,253.90