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	$141.72	8.436%	$153.6755	$153.68	$153.70	$153.70
Purchase #2	$132.54	5.330%	$139.6044	$139.60	$139.60	$139.60
Purchase #3	$136.53	6.139%	$144.9116	$144.91	$144.90	$144.90
Purchase #4	$240.74	9.838%	$264.424	$264.42	$264.40	$264.40
Purchase #5	$97.36	3.257%	$100.531	$100.53	$100.55	$100.50
Purchase #6	$145.86	9.314%	$159.4454	$159.45	$159.45	$159.40
Purchase #7	$151.79	8.732%	$165.0443	$165.04	$165.05	$165.00
7 purchase totals =	$1,046.54		$1,127.6362	$1,127.63	$1,127.65	$1,127.50