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	$157.56	4.146%	$164.0924	$164.09	$164.10	$164.10
Purchase #2	$207.97	10.479%	$229.7632	$229.76	$229.75	$229.80
Purchase #3	$77.52	12.594%	$87.2829	$87.28	$87.30	$87.30
Purchase #4	$157.46	13.833%	$179.2414	$179.24	$179.25	$179.20
Purchase #5	$78.46	4.659%	$82.1155	$82.12	$82.10	$82.10
Purchase #6	$153.84	8.412%	$166.781	$166.78	$166.80	$166.80
Purchase #7	$226.38	5.262%	$238.2921	$238.29	$238.30	$238.30
7 purchase totals =	$1,059.19		$1,147.5685	$1,147.56	$1,147.60	$1,147.60