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	$103.56	4.498%	$108.2181	$108.22	$108.20	$108.20
Purchase #2	$95.51	4.517%	$99.8242	$99.82	$99.80	$99.80
Purchase #3	$143.44	4.233%	$149.5118	$149.51	$149.50	$149.50
Purchase #4	$234.61	3.456%	$242.7181	$242.72	$242.70	$242.70
Purchase #5	$84.32	4.615%	$88.2114	$88.21	$88.20	$88.20
Purchase #6	$175.38	3.698%	$181.8656	$181.87	$181.85	$181.90
Purchase #7	$123.45	9.733%	$135.4654	$135.47	$135.45	$135.50
7 purchase totals =	$960.27		$1,005.8146	$1,005.82	$1,005.70	$1,005.80