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	$232.58	13.416%	$263.7829	$263.78	$263.80	$263.80
Purchase #2	$173.69	5.579%	$183.3802	$183.38	$183.40	$183.40
Purchase #3	$103.46	7.425%	$111.1419	$111.14	$111.15	$111.10
Purchase #4	$82.87	4.168%	$86.324	$86.32	$86.30	$86.30
Purchase #5	$197.59	12.157%	$221.611	$221.61	$221.60	$221.60
Purchase #6	$167.94	13.449%	$190.5263	$190.53	$190.55	$190.50
Purchase #7	$228.77	3.736%	$237.3168	$237.32	$237.30	$237.30
7 purchase totals =	$1,186.90		$1,294.0831	$1,294.08	$1,294.10	$1,294.00