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	$152.28	3.851%	$158.1443	$158.14	$158.15	$158.10
Purchase #2	$48.31	4.240%	$50.3583	$50.36	$50.35	$50.40
Purchase #3	$76.38	8.468%	$82.8479	$82.85	$82.85	$82.80
Purchase #4	$77.53	11.353%	$86.332	$86.33	$86.35	$86.30
Purchase #5	$176.85	6.311%	$188.011	$188.01	$188.00	$188.00
Purchase #6	$186.73	11.382%	$207.9836	$207.98	$208.00	$208.00
Purchase #7	$14.64	5.510%	$15.4467	$15.45	$15.45	$15.40
7 purchase totals =	$732.72		$789.1238	$789.12	$789.15	$789.00