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	$116.64	11.323%	$129.8471	$129.85	$129.85	$129.80
Purchase #2	$90.59	13.857%	$103.1431	$103.14	$103.15	$103.10
Purchase #3	$57.83	4.553%	$60.463	$60.46	$60.45	$60.50
Purchase #4	$164.29	11.760%	$183.6105	$183.61	$183.60	$183.60
Purchase #5	$65.60	13.583%	$74.5104	$74.51	$74.50	$74.50
Purchase #6	$141.50	12.665%	$159.421	$159.42	$159.40	$159.40
Purchase #7	$43.92	7.536%	$47.2298	$47.23	$47.25	$47.20
7 purchase totals =	$680.37		$758.2249	$758.22	$758.20	$758.10