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	$151.87	6.723%	$162.0802	$162.08	$162.10	$162.10
Purchase #2	$55.87	6.252%	$59.363	$59.36	$59.35	$59.40
Purchase #3	$139.95	10.221%	$154.2543	$154.25	$154.25	$154.30
Purchase #4	$13.31	12.561%	$14.9819	$14.98	$15.00	$15.00
Purchase #5	$80.66	11.659%	$90.0641	$90.06	$90.05	$90.10
Purchase #6	$17.48	11.310%	$19.457	$19.46	$19.45	$19.50
Purchase #7	$226.32	11.771%	$252.9601	$252.96	$252.95	$253.00
7 purchase totals =	$685.46		$753.1606	$753.15	$753.15	$753.40