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	$181.87	5.423%	$191.7328	$191.73	$191.75	$191.70
Purchase #2	$111.54	11.485%	$124.3504	$124.35	$124.35	$124.40
Purchase #3	$29.94	9.490%	$32.7813	$32.78	$32.80	$32.80
Purchase #4	$13.76	5.601%	$14.5307	$14.53	$14.55	$14.50
Purchase #5	$145.83	3.785%	$151.3497	$151.35	$151.35	$151.30
Purchase #6	$147.60	13.394%	$167.3695	$167.37	$167.35	$167.40
Purchase #7	$17.50	11.651%	$19.5389	$19.54	$19.55	$19.50
7 purchase totals =	$648.04		$701.6533	$701.65	$701.70	$701.60