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	$198.80	11.751%	$222.161	$222.16	$222.15	$222.20
Purchase #2	$226.30	13.168%	$256.0992	$256.10	$256.10	$256.10
Purchase #3	$174.86	4.298%	$182.3755	$182.38	$182.40	$182.40
Purchase #4	$58.54	11.472%	$65.2557	$65.26	$65.25	$65.30
Purchase #5	$229.62	8.509%	$249.1584	$249.16	$249.15	$249.20
Purchase #6	$108.78	13.385%	$123.3402	$123.34	$123.35	$123.30
Purchase #7	$154.78	12.435%	$174.0269	$174.03	$174.05	$174.00
7 purchase totals =	$1,151.68		$1,272.4169	$1,272.43	$1,272.45	$1,272.50