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	$145.80	5.195%	$153.3743	$153.37	$153.35	$153.40
Purchase #2	$95.76	4.810%	$100.3661	$100.37	$100.35	$100.40
Purchase #3	$236.91	5.722%	$250.466	$250.47	$250.45	$250.50
Purchase #4	$123.56	9.162%	$134.8806	$134.88	$134.90	$134.90
Purchase #5	$171.33	8.410%	$185.7389	$185.74	$185.75	$185.70
Purchase #6	$107.27	12.593%	$120.7785	$120.78	$120.80	$120.80
Purchase #7	$94.42	10.357%	$104.1991	$104.20	$104.20	$104.20
7 purchase totals =	$975.05		$1,049.8035	$1,049.81	$1,049.80	$1,049.90