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	$216.31	9.217%	$236.2473	$236.25	$236.25	$236.20
Purchase #2	$212.47	12.260%	$238.5188	$238.52	$238.50	$238.50
Purchase #3	$181.69	9.744%	$199.3939	$199.39	$199.40	$199.40
Purchase #4	$139.75	9.682%	$153.2806	$153.28	$153.30	$153.30
Purchase #5	$165.37	4.231%	$172.3668	$172.37	$172.35	$172.40
Purchase #6	$47.42	6.160%	$50.3411	$50.34	$50.35	$50.30
Purchase #7	$244.38	11.813%	$273.2486	$273.25	$273.25	$273.20
7 purchase totals =	$1,207.39		$1,323.3971	$1,323.40	$1,323.40	$1,323.30