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	$80.68	8.538%	$87.5685	$87.57	$87.55	$87.60
Purchase #2	$244.62	13.703%	$278.1403	$278.14	$278.15	$278.10
Purchase #3	$108.65	13.750%	$123.5894	$123.59	$123.60	$123.60
Purchase #4	$165.63	11.493%	$184.6659	$184.67	$184.65	$184.70
Purchase #5	$30.92	9.675%	$33.9115	$33.91	$33.90	$33.90
Purchase #6	$164.35	10.648%	$181.85	$181.85	$181.85	$181.90
Purchase #7	$226.71	11.663%	$253.1512	$253.15	$253.15	$253.20
7 purchase totals =	$1,021.56		$1,142.8768	$1,142.88	$1,142.85	$1,143.00