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	$145.61	3.427%	$150.6001	$150.60	$150.60	$150.60
Purchase #2	$143.70	11.262%	$159.8835	$159.88	$159.90	$159.90
Purchase #3	$99.26	6.110%	$105.3248	$105.32	$105.30	$105.30
Purchase #4	$71.72	5.262%	$75.4939	$75.49	$75.50	$75.50
Purchase #5	$216.92	9.388%	$237.2844	$237.28	$237.30	$237.30
Purchase #6	$90.89	6.342%	$96.6542	$96.65	$96.65	$96.70
Purchase #7	$119.50	6.856%	$127.6929	$127.69	$127.70	$127.70
7 purchase totals =	$887.60		$952.9338	$952.91	$952.95	$953.00