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	$90.41	12.418%	$101.6371	$101.64	$101.65	$101.60
Purchase #2	$53.85	11.185%	$59.8731	$59.87	$59.85	$59.90
Purchase #3	$97.28	6.592%	$103.6927	$103.69	$103.70	$103.70
Purchase #4	$155.54	11.529%	$173.4722	$173.47	$173.45	$173.50
Purchase #5	$246.38	10.649%	$272.617	$272.62	$272.60	$272.60
Purchase #6	$237.47	7.204%	$254.5773	$254.58	$254.60	$254.60
Purchase #7	$86.40	3.344%	$89.2892	$89.29	$89.30	$89.30
7 purchase totals =	$967.33		$1,055.1586	$1,055.16	$1,055.15	$1,055.20