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	$73.81	9.590%	$80.8884	$80.89	$80.90	$80.90
Purchase #2	$176.84	11.553%	$197.2703	$197.27	$197.25	$197.30
Purchase #3	$137.65	6.366%	$146.4128	$146.41	$146.40	$146.40
Purchase #4	$92.47	13.721%	$105.1578	$105.16	$105.15	$105.20
Purchase #5	$187.85	4.810%	$196.8856	$196.89	$196.90	$196.90
Purchase #6	$156.74	6.633%	$167.1366	$167.14	$167.15	$167.10
Purchase #7	$143.56	7.752%	$154.6888	$154.69	$154.70	$154.70
7 purchase totals =	$968.92		$1,048.4403	$1,048.45	$1,048.45	$1,048.50