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	$72.29	10.159%	$79.6339	$79.63	$79.65	$79.60
Purchase #2	$74.73	8.264%	$80.9057	$80.91	$80.90	$80.90
Purchase #3	$69.79	10.837%	$77.3531	$77.35	$77.35	$77.40
Purchase #4	$127.40	13.507%	$144.6079	$144.61	$144.60	$144.60
Purchase #5	$250.82	11.481%	$279.6166	$279.62	$279.60	$279.60
Purchase #6	$79.90	13.158%	$90.4132	$90.41	$90.40	$90.40
Purchase #7	$190.35	10.205%	$209.7752	$209.78	$209.80	$209.80
7 purchase totals =	$865.28		$962.3056	$962.31	$962.30	$962.30