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	$172.44	6.275%	$183.2606	$183.26	$183.25	$183.30
Purchase #2	$189.95	13.133%	$214.8961	$214.90	$214.90	$214.90
Purchase #3	$95.82	7.502%	$103.0084	$103.01	$103.00	$103.00
Purchase #4	$78.42	9.286%	$85.7021	$85.70	$85.70	$85.70
Purchase #5	$11.35	13.621%	$12.896	$12.90	$12.90	$12.90
Purchase #6	$166.88	11.365%	$185.8459	$185.85	$185.85	$185.80
Purchase #7	$161.56	12.117%	$181.1362	$181.14	$181.15	$181.10
7 purchase totals =	$876.42		$966.7453	$966.76	$966.75	$966.70