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	$153.81	3.568%	$159.2979	$159.30	$159.30	$159.30
Purchase #2	$40.31	4.806%	$42.2473	$42.25	$42.25	$42.20
Purchase #3	$140.99	6.649%	$150.3644	$150.36	$150.35	$150.40
Purchase #4	$215.78	13.258%	$244.3881	$244.39	$244.40	$244.40
Purchase #5	$122.60	4.131%	$127.6646	$127.66	$127.65	$127.70
Purchase #6	$168.98	10.527%	$186.7685	$186.77	$186.75	$186.80
Purchase #7	$172.29	6.597%	$183.656	$183.66	$183.65	$183.70
7 purchase totals =	$1,014.76		$1,094.3868	$1,094.39	$1,094.35	$1,094.50