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	$241.94	8.701%	$262.9912	$262.99	$263.00	$263.00
Purchase #2	$147.69	8.126%	$159.6913	$159.69	$159.70	$159.70
Purchase #3	$135.30	12.734%	$152.5291	$152.53	$152.55	$152.50
Purchase #4	$51.46	5.700%	$54.3932	$54.39	$54.40	$54.40
Purchase #5	$157.58	9.356%	$172.3232	$172.32	$172.30	$172.30
Purchase #6	$90.45	10.628%	$100.063	$100.06	$100.05	$100.10
Purchase #7	$125.85	12.384%	$141.4353	$141.44	$141.45	$141.40
7 purchase totals =	$950.27		$1,043.4263	$1,043.42	$1,043.45	$1,043.40