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	$33.40	5.386%	$35.1989	$35.20	$35.20	$35.20
Purchase #2	$18.60	5.590%	$19.6397	$19.64	$19.65	$19.60
Purchase #3	$17.80	13.130%	$20.1371	$20.14	$20.15	$20.10
Purchase #4	$37.93	10.865%	$42.0511	$42.05	$42.05	$42.10
Purchase #5	$244.53	13.515%	$277.5782	$277.58	$277.60	$277.60
Purchase #6	$128.87	12.841%	$145.4182	$145.42	$145.40	$145.40
Purchase #7	$44.43	12.674%	$50.0611	$50.06	$50.05	$50.10
7 purchase totals =	$525.56		$590.0843	$590.09	$590.10	$590.10