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	$185.80	10.578%	$205.4539	$205.45	$205.45	$205.50
Purchase #2	$129.25	13.237%	$146.3588	$146.36	$146.35	$146.40
Purchase #3	$37.64	3.602%	$38.9958	$39.00	$39.00	$39.00
Purchase #4	$184.63	11.797%	$206.4108	$206.41	$206.40	$206.40
Purchase #5	$56.90	10.178%	$62.6913	$62.69	$62.70	$62.70
Purchase #6	$151.49	13.618%	$172.1199	$172.12	$172.10	$172.10
Purchase #7	$139.98	8.137%	$151.3702	$151.37	$151.35	$151.40
7 purchase totals =	$885.69		$983.4007	$983.40	$983.35	$983.50