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	$100.92	9.845%	$110.8556	$110.86	$110.85	$110.90
Purchase #2	$151.60	5.704%	$160.2473	$160.25	$160.25	$160.20
Purchase #3	$7.32	13.159%	$8.2832	$8.28	$8.30	$8.30
Purchase #4	$189.84	4.207%	$197.8266	$197.83	$197.85	$197.80
Purchase #5	$126.56	4.159%	$131.8236	$131.82	$131.80	$131.80
Purchase #6	$57.49	3.151%	$59.3015	$59.30	$59.30	$59.30
Purchase #7	$88.66	4.466%	$92.6196	$92.62	$92.60	$92.60
7 purchase totals =	$722.39		$760.9574	$760.96	$760.95	$760.90