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	$181.54	8.127%	$196.2938	$196.29	$196.30	$196.30
Purchase #2	$224.92	13.519%	$255.3269	$255.33	$255.35	$255.30
Purchase #3	$220.76	6.105%	$234.2374	$234.24	$234.25	$234.20
Purchase #4	$61.57	13.410%	$69.8265	$69.83	$69.85	$69.80
Purchase #5	$220.62	9.748%	$242.126	$242.13	$242.15	$242.10
Purchase #6	$94.85	4.378%	$99.0025	$99.00	$99.00	$99.00
Purchase #7	$225.40	6.256%	$239.501	$239.50	$239.50	$239.50
7 purchase totals =	$1,229.66		$1,336.3141	$1,336.32	$1,336.40	$1,336.20