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	$248.71	13.489%	$282.2585	$282.26	$282.25	$282.30
Purchase #2	$85.69	5.202%	$90.1476	$90.15	$90.15	$90.10
Purchase #3	$178.57	11.296%	$198.7413	$198.74	$198.75	$198.70
Purchase #4	$120.91	8.603%	$131.3119	$131.31	$131.30	$131.30
Purchase #5	$91.28	13.278%	$103.4002	$103.40	$103.40	$103.40
Purchase #6	$109.81	6.106%	$116.515	$116.52	$116.50	$116.50
Purchase #7	$214.76	4.510%	$224.4457	$224.45	$224.45	$224.40
7 purchase totals =	$1,049.73		$1,146.8202	$1,146.83	$1,146.80	$1,146.70