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	$76.51	8.687%	$83.1564	$83.16	$83.15	$83.20
Purchase #2	$162.35	10.485%	$179.3724	$179.37	$179.35	$179.40
Purchase #3	$57.38	3.536%	$59.409	$59.41	$59.40	$59.40
Purchase #4	$158.56	6.661%	$169.1217	$169.12	$169.10	$169.10
Purchase #5	$106.42	5.381%	$112.1465	$112.15	$112.15	$112.10
Purchase #6	$238.41	3.726%	$247.2932	$247.29	$247.30	$247.30
Purchase #7	$10.71	11.407%	$11.9317	$11.93	$11.95	$11.90
7 purchase totals =	$810.34		$862.4309	$862.43	$862.40	$862.40