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	$169.40	3.169%	$174.7683	$174.77	$174.75	$174.80
Purchase #2	$138.91	4.787%	$145.5596	$145.56	$145.55	$145.60
Purchase #3	$216.39	7.698%	$233.0477	$233.05	$233.05	$233.00
Purchase #4	$88.46	13.578%	$100.4711	$100.47	$100.45	$100.50
Purchase #5	$127.87	5.161%	$134.4694	$134.47	$134.45	$134.50
Purchase #6	$10.40	8.620%	$11.2965	$11.30	$11.30	$11.30
Purchase #7	$216.48	5.210%	$227.7586	$227.76	$227.75	$227.80
7 purchase totals =	$967.91		$1,027.3712	$1,027.38	$1,027.30	$1,027.50