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	$238.76	10.576%	$264.0113	$264.01	$264.00	$264.00
Purchase #2	$64.52	11.663%	$72.045	$72.05	$72.05	$72.00
Purchase #3	$42.83	6.381%	$45.563	$45.56	$45.55	$45.60
Purchase #4	$192.75	9.248%	$210.5755	$210.58	$210.60	$210.60
Purchase #5	$41.89	9.321%	$45.7946	$45.79	$45.80	$45.80
Purchase #6	$90.70	5.572%	$95.7538	$95.75	$95.75	$95.80
Purchase #7	$46.33	4.316%	$48.3296	$48.33	$48.35	$48.30
7 purchase totals =	$717.78		$782.0728	$782.07	$782.10	$782.10