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	$161.90	6.738%	$172.8088	$172.81	$172.80	$172.80
Purchase #2	$242.80	10.151%	$267.4466	$267.45	$267.45	$267.40
Purchase #3	$188.68	9.281%	$206.1914	$206.19	$206.20	$206.20
Purchase #4	$250.67	4.541%	$262.0529	$262.05	$262.05	$262.10
Purchase #5	$54.25	9.847%	$59.592	$59.59	$59.60	$59.60
Purchase #6	$120.45	9.355%	$131.7181	$131.72	$131.70	$131.70
Purchase #7	$140.27	8.680%	$152.4454	$152.45	$152.45	$152.40
7 purchase totals =	$1,159.02		$1,252.2552	$1,252.26	$1,252.25	$1,252.20