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	$249.34	9.342%	$272.6333	$272.63	$272.65	$272.60
Purchase #2	$15.46	13.578%	$17.5592	$17.56	$17.55	$17.60
Purchase #3	$79.89	13.639%	$90.7862	$90.79	$90.80	$90.80
Purchase #4	$142.52	6.791%	$152.1985	$152.20	$152.20	$152.20
Purchase #5	$53.80	3.605%	$55.7395	$55.74	$55.75	$55.70
Purchase #6	$40.42	5.403%	$42.6039	$42.60	$42.60	$42.60
Purchase #7	$237.86	6.366%	$253.0022	$253.00	$253.00	$253.00
7 purchase totals =	$819.29		$884.5228	$884.52	$884.55	$884.50