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	$138.89	12.771%	$156.6276	$156.63	$156.65	$156.60
Purchase #2	$34.73	7.852%	$37.457	$37.46	$37.45	$37.50
Purchase #3	$249.40	13.715%	$283.6052	$283.61	$283.60	$283.60
Purchase #4	$99.65	11.659%	$111.2682	$111.27	$111.25	$111.30
Purchase #5	$155.70	13.123%	$176.1325	$176.13	$176.15	$176.10
Purchase #6	$52.80	5.170%	$55.5298	$55.53	$55.55	$55.50
Purchase #7	$233.56	4.225%	$243.4279	$243.43	$243.45	$243.40
7 purchase totals =	$964.73		$1,064.0482	$1,064.06	$1,064.10	$1,064.00