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	$245.99	6.142%	$261.0987	$261.10	$261.10	$261.10
Purchase #2	$159.67	3.803%	$165.7423	$165.74	$165.75	$165.70
Purchase #3	$223.45	4.691%	$233.932	$233.93	$233.95	$233.90
Purchase #4	$152.43	12.214%	$171.0478	$171.05	$171.05	$171.00
Purchase #5	$55.70	10.395%	$61.49	$61.49	$61.50	$61.50
Purchase #6	$37.92	11.865%	$42.4192	$42.42	$42.40	$42.40
Purchase #7	$60.65	13.298%	$68.7152	$68.72	$68.70	$68.70
7 purchase totals =	$935.81		$1,004.4452	$1,004.45	$1,004.45	$1,004.30