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	$206.36	7.869%	$222.5985	$222.60	$222.60	$222.60
Purchase #2	$110.75	5.392%	$116.7216	$116.72	$116.70	$116.70
Purchase #3	$236.40	11.560%	$263.7278	$263.73	$263.75	$263.70
Purchase #4	$50.72	11.244%	$56.423	$56.42	$56.40	$56.40
Purchase #5	$246.27	6.621%	$262.5755	$262.58	$262.60	$262.60
Purchase #6	$138.26	4.321%	$144.2342	$144.23	$144.25	$144.20
Purchase #7	$130.74	10.376%	$144.3056	$144.31	$144.30	$144.30
7 purchase totals =	$1,119.50		$1,210.5862	$1,210.59	$1,210.60	$1,210.50