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	$92.68	11.606%	$103.4364	$103.44	$103.45	$103.40
Purchase #2	$240.86	7.304%	$258.4524	$258.45	$258.45	$258.50
Purchase #3	$49.44	7.778%	$53.2854	$53.29	$53.30	$53.30
Purchase #4	$60.40	6.369%	$64.2469	$64.25	$64.25	$64.20
Purchase #5	$159.27	8.184%	$172.3047	$172.30	$172.30	$172.30
Purchase #6	$196.28	13.280%	$222.346	$222.35	$222.35	$222.30
Purchase #7	$20.40	5.593%	$21.541	$21.54	$21.55	$21.50
7 purchase totals =	$819.33		$895.6128	$895.62	$895.65	$895.50