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	$156.54	10.154%	$172.4351	$172.44	$172.45	$172.40
Purchase #2	$234.62	12.851%	$264.771	$264.77	$264.75	$264.80
Purchase #3	$160.96	11.695%	$179.7843	$179.78	$179.80	$179.80
Purchase #4	$77.70	10.249%	$85.6635	$85.66	$85.65	$85.70
Purchase #5	$100.99	12.684%	$113.7996	$113.80	$113.80	$113.80
Purchase #6	$207.85	6.555%	$221.4746	$221.47	$221.45	$221.50
Purchase #7	$94.38	11.569%	$105.2988	$105.30	$105.30	$105.30
7 purchase totals =	$1,033.04		$1,143.2269	$1,143.22	$1,143.20	$1,143.30