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	$86.52	3.381%	$89.4452	$89.45	$89.45	$89.40
Purchase #2	$171.87	13.653%	$195.3354	$195.34	$195.35	$195.30
Purchase #3	$7.54	7.861%	$8.1327	$8.13	$8.15	$8.10
Purchase #4	$175.69	11.690%	$196.2282	$196.23	$196.25	$196.20
Purchase #5	$12.34	10.784%	$13.6707	$13.67	$13.65	$13.70
Purchase #6	$106.28	11.265%	$118.2524	$118.25	$118.25	$118.30
Purchase #7	$173.53	12.507%	$195.2334	$195.23	$195.25	$195.20
7 purchase totals =	$733.77		$816.2980	$816.30	$816.35	$816.20