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	$193.55	8.759%	$210.503	$210.50	$210.50	$210.50
Purchase #2	$238.46	7.321%	$255.9177	$255.92	$255.90	$255.90
Purchase #3	$41.38	10.240%	$45.6173	$45.62	$45.60	$45.60
Purchase #4	$172.67	5.730%	$182.564	$182.56	$182.55	$182.60
Purchase #5	$40.53	5.205%	$42.6396	$42.64	$42.65	$42.60
Purchase #6	$172.37	3.311%	$178.0772	$178.08	$178.10	$178.10
Purchase #7	$157.50	6.777%	$168.1738	$168.17	$168.15	$168.20
7 purchase totals =	$1,016.46		$1,083.4926	$1,083.49	$1,083.45	$1,083.50