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	$242.42	12.445%	$272.5892	$272.59	$272.60	$272.60
Purchase #2	$242.90	13.687%	$276.1457	$276.15	$276.15	$276.10
Purchase #3	$126.90	3.407%	$131.2235	$131.22	$131.20	$131.20
Purchase #4	$151.49	3.262%	$156.4316	$156.43	$156.45	$156.40
Purchase #5	$132.63	12.396%	$149.0708	$149.07	$149.05	$149.10
Purchase #6	$107.42	3.845%	$111.5503	$111.55	$111.55	$111.60
Purchase #7	$90.98	7.872%	$98.1419	$98.14	$98.15	$98.10
7 purchase totals =	$1,094.74		$1,195.1530	$1,195.15	$1,195.15	$1,195.10