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	$187.75	11.374%	$209.1047	$209.10	$209.10	$209.10
Purchase #2	$51.33	6.182%	$54.5032	$54.50	$54.50	$54.50
Purchase #3	$175.92	5.309%	$185.2596	$185.26	$185.25	$185.30
Purchase #4	$198.71	10.589%	$219.7514	$219.75	$219.75	$219.80
Purchase #5	$235.41	4.752%	$246.5967	$246.60	$246.60	$246.60
Purchase #6	$129.64	12.761%	$146.1834	$146.18	$146.20	$146.20
Purchase #7	$18.97	5.749%	$20.0606	$20.06	$20.05	$20.10
7 purchase totals =	$997.73		$1,081.4596	$1,081.45	$1,081.45	$1,081.60