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	$241.91	7.553%	$260.1815	$260.18	$260.20	$260.20
Purchase #2	$186.53	7.368%	$200.2735	$200.27	$200.25	$200.30
Purchase #3	$46.61	7.533%	$50.1211	$50.12	$50.10	$50.10
Purchase #4	$157.64	4.837%	$165.265	$165.27	$165.25	$165.30
Purchase #5	$200.77	12.456%	$225.7779	$225.78	$225.80	$225.80
Purchase #6	$238.42	6.815%	$254.6683	$254.67	$254.65	$254.70
Purchase #7	$154.47	11.694%	$172.5337	$172.53	$172.55	$172.50
7 purchase totals =	$1,226.35		$1,328.8210	$1,328.82	$1,328.80	$1,328.90