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	$65.73	10.737%	$72.7874	$72.79	$72.80	$72.80
Purchase #2	$18.66	3.737%	$19.3573	$19.36	$19.35	$19.40
Purchase #3	$163.28	6.734%	$174.2753	$174.28	$174.30	$174.30
Purchase #4	$94.72	9.501%	$103.7193	$103.72	$103.70	$103.70
Purchase #5	$221.31	7.792%	$238.5545	$238.55	$238.55	$238.60
Purchase #6	$9.73	4.712%	$10.1885	$10.19	$10.20	$10.20
Purchase #7	$61.42	7.658%	$66.1235	$66.12	$66.10	$66.10
7 purchase totals =	$634.85		$685.0058	$685.01	$685.00	$685.10