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	$33.67	7.574%	$36.2202	$36.22	$36.20	$36.20
Purchase #2	$118.60	11.336%	$132.0445	$132.04	$132.05	$132.00
Purchase #3	$56.93	10.189%	$62.7306	$62.73	$62.75	$62.70
Purchase #4	$212.75	9.666%	$233.3144	$233.31	$233.30	$233.30
Purchase #5	$160.93	9.224%	$175.7742	$175.77	$175.75	$175.80
Purchase #6	$185.47	10.739%	$205.3876	$205.39	$205.40	$205.40
Purchase #7	$243.42	4.862%	$255.2551	$255.26	$255.25	$255.30
7 purchase totals =	$1,011.77		$1,100.7266	$1,100.72	$1,100.70	$1,100.70