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	$150.98	4.661%	$158.0172	$158.02	$158.00	$158.00
Purchase #2	$108.81	13.468%	$123.4645	$123.46	$123.45	$123.50
Purchase #3	$172.64	6.737%	$184.2708	$184.27	$184.25	$184.30
Purchase #4	$89.46	13.239%	$101.3036	$101.30	$101.30	$101.30
Purchase #5	$245.67	11.844%	$274.7672	$274.77	$274.75	$274.80
Purchase #6	$210.60	12.379%	$236.6702	$236.67	$236.65	$236.70
Purchase #7	$188.68	4.162%	$196.5329	$196.53	$196.55	$196.50
7 purchase totals =	$1,166.84		$1,275.0264	$1,275.02	$1,274.95	$1,275.10