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	$117.96	8.413%	$127.884	$127.88	$127.90	$127.90
Purchase #2	$8.27	5.682%	$8.7399	$8.74	$8.75	$8.70
Purchase #3	$152.33	4.293%	$158.8695	$158.87	$158.85	$158.90
Purchase #4	$34.45	10.577%	$38.0938	$38.09	$38.10	$38.10
Purchase #5	$54.53	8.424%	$59.1236	$59.12	$59.10	$59.10
Purchase #6	$227.62	10.558%	$251.6521	$251.65	$251.65	$251.70
Purchase #7	$90.30	10.204%	$99.5142	$99.51	$99.50	$99.50
7 purchase totals =	$685.46		$743.8771	$743.86	$743.85	$743.90