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	$206.81	7.684%	$222.7013	$222.70	$222.70	$222.70
Purchase #2	$217.41	11.822%	$243.1122	$243.11	$243.10	$243.10
Purchase #3	$44.79	9.261%	$48.938	$48.94	$48.95	$48.90
Purchase #4	$18.90	10.727%	$20.9274	$20.93	$20.95	$20.90
Purchase #5	$37.27	10.589%	$41.2165	$41.22	$41.20	$41.20
Purchase #6	$169.73	4.251%	$176.9452	$176.95	$176.95	$176.90
Purchase #7	$222.83	12.381%	$250.4186	$250.42	$250.40	$250.40
7 purchase totals =	$917.74		$1,004.2592	$1,004.27	$1,004.25	$1,004.10