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	$114.42	7.644%	$123.1663	$123.17	$123.15	$123.20
Purchase #2	$27.70	7.717%	$29.8376	$29.84	$29.85	$29.80
Purchase #3	$80.88	11.162%	$89.9078	$89.91	$89.90	$89.90
Purchase #4	$144.66	11.127%	$160.7563	$160.76	$160.75	$160.80
Purchase #5	$151.59	13.737%	$172.4139	$172.41	$172.40	$172.40
Purchase #6	$140.49	4.601%	$146.9539	$146.95	$146.95	$147.00
Purchase #7	$241.31	13.622%	$274.1812	$274.18	$274.20	$274.20
7 purchase totals =	$901.05		$997.2170	$997.22	$997.20	$997.30