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	$244.43	4.561%	$255.5785	$255.58	$255.60	$255.60
Purchase #2	$233.62	12.193%	$262.1053	$262.11	$262.10	$262.10
Purchase #3	$209.85	4.113%	$218.4811	$218.48	$218.50	$218.50
Purchase #4	$80.40	9.608%	$88.1248	$88.12	$88.10	$88.10
Purchase #5	$34.67	9.153%	$37.8433	$37.84	$37.85	$37.80
Purchase #6	$138.93	5.457%	$146.5114	$146.51	$146.50	$146.50
Purchase #7	$242.33	7.236%	$259.865	$259.87	$259.85	$259.90
7 purchase totals =	$1,184.23		$1,268.5094	$1,268.51	$1,268.50	$1,268.50