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	$185.89	4.595%	$194.4316	$194.43	$194.45	$194.40
Purchase #2	$137.72	9.708%	$151.0899	$151.09	$151.10	$151.10
Purchase #3	$239.83	4.201%	$249.9053	$249.91	$249.90	$249.90
Purchase #4	$44.98	7.739%	$48.461	$48.46	$48.45	$48.50
Purchase #5	$92.74	4.846%	$97.2342	$97.23	$97.25	$97.20
Purchase #6	$108.37	7.475%	$116.4707	$116.47	$116.45	$116.50
Purchase #7	$98.41	13.169%	$111.3696	$111.37	$111.35	$111.40
7 purchase totals =	$907.94		$968.9623	$968.96	$968.95	$969.00