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	$114.95	13.697%	$130.6947	$130.69	$130.70	$130.70
Purchase #2	$135.50	7.322%	$145.4213	$145.42	$145.40	$145.40
Purchase #3	$146.48	4.667%	$153.3162	$153.32	$153.30	$153.30
Purchase #4	$165.64	6.366%	$176.1846	$176.18	$176.20	$176.20
Purchase #5	$55.28	7.525%	$59.4398	$59.44	$59.45	$59.40
Purchase #6	$47.46	7.463%	$51.0019	$51.00	$51.00	$51.00
Purchase #7	$243.43	7.729%	$262.2447	$262.24	$262.25	$262.20
7 purchase totals =	$908.74		$978.3032	$978.29	$978.30	$978.20