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	$220.68	3.441%	$228.2736	$228.27	$228.25	$228.30
Purchase #2	$139.31	9.837%	$153.0139	$153.01	$153.00	$153.00
Purchase #3	$234.85	12.688%	$264.6478	$264.65	$264.65	$264.60
Purchase #4	$128.46	8.237%	$139.0413	$139.04	$139.05	$139.00
Purchase #5	$114.30	10.475%	$126.2729	$126.27	$126.25	$126.30
Purchase #6	$160.62	11.738%	$179.4736	$179.47	$179.45	$179.50
Purchase #7	$166.48	3.805%	$172.8146	$172.81	$172.80	$172.80
7 purchase totals =	$1,164.70		$1,263.5377	$1,263.52	$1,263.45	$1,263.50