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	$100.78	3.738%	$104.5472	$104.55	$104.55	$104.50
Purchase #2	$176.76	8.611%	$191.9808	$191.98	$192.00	$192.00
Purchase #3	$34.72	6.422%	$36.9497	$36.95	$36.95	$36.90
Purchase #4	$44.88	3.707%	$46.5437	$46.54	$46.55	$46.50
Purchase #5	$224.52	3.161%	$231.6171	$231.62	$231.60	$231.60
Purchase #6	$208.32	9.669%	$228.4625	$228.46	$228.45	$228.50
Purchase #7	$233.75	13.506%	$265.3203	$265.32	$265.30	$265.30
7 purchase totals =	$1,023.73		$1,105.4213	$1,105.42	$1,105.40	$1,105.30