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	$217.61	3.827%	$225.9379	$225.94	$225.95	$225.90
Purchase #2	$229.94	13.719%	$261.4855	$261.49	$261.50	$261.50
Purchase #3	$123.92	13.667%	$140.8561	$140.86	$140.85	$140.90
Purchase #4	$53.61	13.370%	$60.7777	$60.78	$60.80	$60.80
Purchase #5	$135.91	10.539%	$150.2336	$150.23	$150.25	$150.20
Purchase #6	$22.42	11.828%	$25.0718	$25.07	$25.05	$25.10
Purchase #7	$175.88	5.827%	$186.1285	$186.13	$186.15	$186.10
7 purchase totals =	$959.29		$1,050.4911	$1,050.50	$1,050.55	$1,050.50