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	$160.62	7.341%	$172.4111	$172.41	$172.40	$172.40
Purchase #2	$161.69	13.825%	$184.0436	$184.04	$184.05	$184.00
Purchase #3	$57.89	13.690%	$65.8151	$65.82	$65.80	$65.80
Purchase #4	$9.72	3.693%	$10.079	$10.08	$10.10	$10.10
Purchase #5	$22.95	11.710%	$25.6374	$25.64	$25.65	$25.60
Purchase #6	$72.86	7.490%	$78.3172	$78.32	$78.30	$78.30
Purchase #7	$243.97	10.441%	$269.4429	$269.44	$269.45	$269.40
7 purchase totals =	$729.70		$805.7463	$805.75	$805.75	$805.60