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	$229.45	6.753%	$244.9448	$244.94	$244.95	$244.90
Purchase #2	$208.83	7.500%	$224.4923	$224.49	$224.50	$224.50
Purchase #3	$80.72	11.463%	$89.9729	$89.97	$89.95	$90.00
Purchase #4	$63.56	4.184%	$66.2194	$66.22	$66.20	$66.20
Purchase #5	$76.78	8.460%	$83.2756	$83.28	$83.30	$83.30
Purchase #6	$141.70	11.769%	$158.3767	$158.38	$158.40	$158.40
Purchase #7	$179.60	7.157%	$192.454	$192.45	$192.45	$192.50
7 purchase totals =	$980.64		$1,059.7357	$1,059.73	$1,059.75	$1,059.80