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	$100.59	4.435%	$105.0512	$105.05	$105.05	$105.10
Purchase #2	$52.43	5.763%	$55.4515	$55.45	$55.45	$55.50
Purchase #3	$153.97	11.456%	$171.6088	$171.61	$171.60	$171.60
Purchase #4	$41.58	13.272%	$47.0985	$47.10	$47.10	$47.10
Purchase #5	$180.38	6.844%	$192.7252	$192.73	$192.75	$192.70
Purchase #6	$211.72	8.607%	$229.9427	$229.94	$229.95	$229.90
Purchase #7	$11.34	9.435%	$12.4099	$12.41	$12.40	$12.40
7 purchase totals =	$752.01		$814.2878	$814.29	$814.30	$814.30