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	$179.83	10.631%	$198.9477	$198.95	$198.95	$198.90
Purchase #2	$233.49	9.309%	$255.2256	$255.23	$255.25	$255.20
Purchase #3	$146.40	9.495%	$160.3007	$160.30	$160.30	$160.30
Purchase #4	$92.83	10.781%	$102.838	$102.84	$102.85	$102.80
Purchase #5	$136.54	7.308%	$146.5183	$146.52	$146.50	$146.50
Purchase #6	$95.83	10.275%	$105.6765	$105.68	$105.70	$105.70
Purchase #7	$168.77	6.102%	$179.0683	$179.07	$179.05	$179.10
7 purchase totals =	$1,053.69		$1,148.5751	$1,148.59	$1,148.60	$1,148.50