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	$119.52	3.200%	$123.3446	$123.34	$123.35	$123.30
Purchase #2	$227.79	10.747%	$252.2706	$252.27	$252.25	$252.30
Purchase #3	$183.74	11.581%	$205.0189	$205.02	$205.00	$205.00
Purchase #4	$173.54	4.361%	$181.1081	$181.11	$181.10	$181.10
Purchase #5	$97.37	8.318%	$105.4692	$105.47	$105.45	$105.50
Purchase #6	$183.62	4.495%	$191.8737	$191.87	$191.85	$191.90
Purchase #7	$99.95	5.338%	$105.2853	$105.29	$105.30	$105.30
7 purchase totals =	$1,085.53		$1,164.3704	$1,164.37	$1,164.30	$1,164.40