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	$216.80	11.733%	$242.2371	$242.24	$242.25	$242.20
Purchase #2	$28.93	8.113%	$31.2771	$31.28	$31.30	$31.30
Purchase #3	$44.74	10.397%	$49.3916	$49.39	$49.40	$49.40
Purchase #4	$103.46	7.405%	$111.1212	$111.12	$111.10	$111.10
Purchase #5	$203.93	4.361%	$212.8234	$212.82	$212.80	$212.80
Purchase #6	$234.84	9.215%	$256.4805	$256.48	$256.50	$256.50
Purchase #7	$157.83	7.804%	$170.1471	$170.15	$170.15	$170.10
7 purchase totals =	$990.53		$1,073.4780	$1,073.48	$1,073.50	$1,073.40