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	$156.52	5.653%	$165.3681	$165.37	$165.35	$165.40
Purchase #2	$218.50	4.830%	$229.0536	$229.05	$229.05	$229.10
Purchase #3	$194.74	6.806%	$207.994	$207.99	$208.00	$208.00
Purchase #4	$200.64	13.779%	$228.2862	$228.29	$228.30	$228.30
Purchase #5	$100.63	12.105%	$112.8113	$112.81	$112.80	$112.80
Purchase #6	$170.81	10.251%	$188.3197	$188.32	$188.30	$188.30
Purchase #7	$115.50	6.859%	$123.4221	$123.42	$123.40	$123.40
7 purchase totals =	$1,157.34		$1,255.2550	$1,255.25	$1,255.20	$1,255.30