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	$117.72	9.160%	$128.5032	$128.50	$128.50	$128.50
Purchase #2	$209.37	13.407%	$237.4402	$237.44	$237.45	$237.40
Purchase #3	$200.82	4.496%	$209.8489	$209.85	$209.85	$209.80
Purchase #4	$89.85	10.188%	$99.0039	$99.00	$99.00	$99.00
Purchase #5	$46.50	9.277%	$50.8138	$50.81	$50.80	$50.80
Purchase #6	$230.87	9.279%	$252.2924	$252.29	$252.30	$252.30
Purchase #7	$23.33	3.261%	$24.0908	$24.09	$24.10	$24.10
7 purchase totals =	$918.46		$1,001.9932	$1,001.98	$1,002.00	$1,001.90