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	$218.88	13.502%	$248.4332	$248.43	$248.45	$248.40
Purchase #2	$96.58	8.595%	$104.8811	$104.88	$104.90	$104.90
Purchase #3	$134.89	6.336%	$143.4366	$143.44	$143.45	$143.40
Purchase #4	$200.64	10.391%	$221.4885	$221.49	$221.50	$221.50
Purchase #5	$219.26	10.673%	$242.6616	$242.66	$242.65	$242.70
Purchase #6	$78.89	11.849%	$88.2377	$88.24	$88.25	$88.20
Purchase #7	$34.29	13.483%	$38.9133	$38.91	$38.90	$38.90
7 purchase totals =	$983.43		$1,088.0520	$1,088.05	$1,088.10	$1,088.00