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	$124.74	11.495%	$139.0789	$139.08	$139.10	$139.10
Purchase #2	$11.83	8.760%	$12.8663	$12.87	$12.85	$12.90
Purchase #3	$229.66	11.805%	$256.7714	$256.77	$256.75	$256.80
Purchase #4	$134.99	5.239%	$142.0621	$142.06	$142.05	$142.10
Purchase #5	$145.39	4.846%	$152.4356	$152.44	$152.45	$152.40
Purchase #6	$109.61	10.297%	$120.8965	$120.90	$120.90	$120.90
Purchase #7	$219.88	12.495%	$247.354	$247.35	$247.35	$247.40
7 purchase totals =	$976.10		$1,071.4648	$1,071.47	$1,071.45	$1,071.60