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	$194.91	13.515%	$221.2521	$221.25	$221.25	$221.30
Purchase #2	$214.26	3.351%	$221.4399	$221.44	$221.45	$221.40
Purchase #3	$224.34	5.784%	$237.3158	$237.32	$237.30	$237.30
Purchase #4	$27.62	6.399%	$29.3874	$29.39	$29.40	$29.40
Purchase #5	$224.59	13.547%	$255.0152	$255.02	$255.00	$255.00
Purchase #6	$37.57	13.414%	$42.6096	$42.61	$42.60	$42.60
Purchase #7	$53.76	12.139%	$60.2859	$60.29	$60.30	$60.30
7 purchase totals =	$977.05		$1,067.3059	$1,067.32	$1,067.30	$1,067.30