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	$212.79	11.474%	$237.2055	$237.21	$237.20	$237.20
Purchase #2	$210.55	10.137%	$231.8935	$231.89	$231.90	$231.90
Purchase #3	$100.73	10.566%	$111.3731	$111.37	$111.35	$111.40
Purchase #4	$49.80	9.396%	$54.4792	$54.48	$54.50	$54.50
Purchase #5	$19.46	10.806%	$21.5628	$21.56	$21.55	$21.60
Purchase #6	$160.64	4.548%	$167.9459	$167.95	$167.95	$167.90
Purchase #7	$73.51	4.382%	$76.7312	$76.73	$76.75	$76.70
7 purchase totals =	$827.48		$901.1912	$901.19	$901.20	$901.20