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	$49.68	8.512%	$53.9088	$53.91	$53.90	$53.90
Purchase #2	$138.52	3.541%	$143.425	$143.43	$143.45	$143.40
Purchase #3	$181.72	7.310%	$195.0037	$195.00	$195.00	$195.00
Purchase #4	$172.77	10.177%	$190.3528	$190.35	$190.35	$190.40
Purchase #5	$96.82	13.179%	$109.5799	$109.58	$109.60	$109.60
Purchase #6	$212.32	4.649%	$222.1908	$222.19	$222.20	$222.20
Purchase #7	$95.86	9.620%	$105.0817	$105.08	$105.10	$105.10
7 purchase totals =	$947.69		$1,019.5427	$1,019.54	$1,019.60	$1,019.60