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	$208.74	9.607%	$228.7937	$228.79	$228.80	$228.80
Purchase #2	$48.40	13.202%	$54.7898	$54.79	$54.80	$54.80
Purchase #3	$55.56	6.719%	$59.2931	$59.29	$59.30	$59.30
Purchase #4	$199.95	6.475%	$212.8968	$212.90	$212.90	$212.90
Purchase #5	$49.88	11.176%	$55.4546	$55.45	$55.45	$55.50
Purchase #6	$167.33	5.749%	$176.9498	$176.95	$176.95	$176.90
Purchase #7	$23.98	13.530%	$27.2245	$27.22	$27.20	$27.20
7 purchase totals =	$753.84		$815.4023	$815.39	$815.40	$815.40