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	$111.54	7.389%	$119.7817	$119.78	$119.80	$119.80
Purchase #2	$66.55	9.168%	$72.6513	$72.65	$72.65	$72.70
Purchase #3	$197.88	13.273%	$224.1446	$224.14	$224.15	$224.10
Purchase #4	$181.87	4.253%	$189.6049	$189.60	$189.60	$189.60
Purchase #5	$176.68	11.491%	$196.9823	$196.98	$197.00	$197.00
Purchase #6	$87.59	12.230%	$98.3023	$98.30	$98.30	$98.30
Purchase #7	$149.28	11.819%	$166.9234	$166.92	$166.90	$166.90
7 purchase totals =	$971.39		$1,068.3905	$1,068.37	$1,068.40	$1,068.40