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	$145.84	8.870%	$158.776	$158.78	$158.80	$158.80
Purchase #2	$99.39	12.444%	$111.7581	$111.76	$111.75	$111.80
Purchase #3	$142.87	13.296%	$161.866	$161.87	$161.85	$161.90
Purchase #4	$44.25	4.683%	$46.3222	$46.32	$46.30	$46.30
Purchase #5	$215.44	4.121%	$224.3183	$224.32	$224.30	$224.30
Purchase #6	$85.54	8.437%	$92.757	$92.76	$92.75	$92.80
Purchase #7	$203.72	3.620%	$211.0947	$211.09	$211.10	$211.10
7 purchase totals =	$937.05		$1,006.8923	$1,006.90	$1,006.85	$1,007.00