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	$122.68	10.750%	$135.8681	$135.87	$135.85	$135.90
Purchase #2	$83.65	6.232%	$88.8631	$88.86	$88.85	$88.90
Purchase #3	$103.86	4.558%	$108.5939	$108.59	$108.60	$108.60
Purchase #4	$95.93	8.348%	$103.9382	$103.94	$103.95	$103.90
Purchase #5	$240.57	7.665%	$259.0097	$259.01	$259.00	$259.00
Purchase #6	$92.73	7.871%	$100.0288	$100.03	$100.05	$100.00
Purchase #7	$230.40	11.181%	$256.161	$256.16	$256.15	$256.20
7 purchase totals =	$969.82		$1,052.4628	$1,052.46	$1,052.45	$1,052.50