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	$151.68	10.837%	$168.1176	$168.12	$168.10	$168.10
Purchase #2	$40.87	4.348%	$42.647	$42.65	$42.65	$42.60
Purchase #3	$75.34	4.114%	$78.4395	$78.44	$78.45	$78.40
Purchase #4	$37.93	7.387%	$40.7319	$40.73	$40.75	$40.70
Purchase #5	$242.62	4.433%	$253.3753	$253.38	$253.40	$253.40
Purchase #6	$198.74	10.826%	$220.2556	$220.26	$220.25	$220.30
Purchase #7	$151.73	4.690%	$158.8461	$158.85	$158.85	$158.80
7 purchase totals =	$898.91		$962.4130	$962.43	$962.45	$962.30