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	$67.53	10.388%	$74.545	$74.55	$74.55	$74.50
Purchase #2	$162.47	6.173%	$172.4993	$172.50	$172.50	$172.50
Purchase #3	$76.62	8.501%	$83.1335	$83.13	$83.15	$83.10
Purchase #4	$181.80	3.163%	$187.5503	$187.55	$187.55	$187.60
Purchase #5	$146.41	9.243%	$159.9427	$159.94	$159.95	$159.90
Purchase #6	$75.62	9.612%	$82.8886	$82.89	$82.90	$82.90
Purchase #7	$249.78	3.622%	$258.827	$258.83	$258.85	$258.80
7 purchase totals =	$960.23		$1,019.3864	$1,019.39	$1,019.45	$1,019.30