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	$182.36	3.445%	$188.6423	$188.64	$188.65	$188.60
Purchase #2	$109.69	12.505%	$123.4067	$123.41	$123.40	$123.40
Purchase #3	$142.81	7.407%	$153.3879	$153.39	$153.40	$153.40
Purchase #4	$145.31	8.816%	$158.1205	$158.12	$158.10	$158.10
Purchase #5	$226.26	4.244%	$235.8625	$235.86	$235.85	$235.90
Purchase #6	$139.93	9.392%	$153.0722	$153.07	$153.05	$153.10
Purchase #7	$198.52	6.253%	$210.9335	$210.93	$210.95	$210.90
7 purchase totals =	$1,144.88		$1,223.4256	$1,223.42	$1,223.40	$1,223.40