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	$137.55	10.601%	$152.1317	$152.13	$152.15	$152.10
Purchase #2	$137.54	8.212%	$148.8348	$148.83	$148.85	$148.80
Purchase #3	$144.87	13.336%	$164.1899	$164.19	$164.20	$164.20
Purchase #4	$154.49	7.388%	$165.9037	$165.90	$165.90	$165.90
Purchase #5	$187.76	8.434%	$203.5957	$203.60	$203.60	$203.60
Purchase #6	$130.54	9.128%	$142.4557	$142.46	$142.45	$142.50
Purchase #7	$215.70	8.158%	$233.2968	$233.30	$233.30	$233.30
7 purchase totals =	$1,108.45		$1,210.4083	$1,210.41	$1,210.45	$1,210.40