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	$86.92	8.379%	$94.203	$94.20	$94.20	$94.20
Purchase #2	$154.99	11.182%	$172.321	$172.32	$172.30	$172.30
Purchase #3	$101.61	3.498%	$105.1643	$105.16	$105.15	$105.20
Purchase #4	$40.44	11.655%	$45.1533	$45.15	$45.15	$45.20
Purchase #5	$187.31	4.652%	$196.0237	$196.02	$196.00	$196.00
Purchase #6	$225.50	5.215%	$237.2598	$237.26	$237.25	$237.30
Purchase #7	$197.33	12.264%	$221.5306	$221.53	$221.55	$221.50
7 purchase totals =	$994.10		$1,071.6557	$1,071.64	$1,071.60	$1,071.70