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	$151.61	13.778%	$172.4988	$172.50	$172.50	$172.50
Purchase #2	$37.93	8.335%	$41.0915	$41.09	$41.10	$41.10
Purchase #3	$29.46	12.689%	$33.1982	$33.20	$33.20	$33.20
Purchase #4	$72.86	3.656%	$75.5238	$75.52	$75.50	$75.50
Purchase #5	$142.70	6.699%	$152.2595	$152.26	$152.25	$152.30
Purchase #6	$244.55	13.501%	$277.5667	$277.57	$277.55	$277.60
Purchase #7	$162.50	13.539%	$184.5009	$184.50	$184.50	$184.50
7 purchase totals =	$841.61		$936.6394	$936.64	$936.60	$936.70