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	$130.63	7.727%	$140.7238	$140.72	$140.70	$140.70
Purchase #2	$193.46	7.242%	$207.4704	$207.47	$207.45	$207.50
Purchase #3	$117.94	10.245%	$130.023	$130.02	$130.00	$130.00
Purchase #4	$73.55	5.865%	$77.8637	$77.86	$77.85	$77.90
Purchase #5	$119.88	8.495%	$130.0638	$130.06	$130.05	$130.10
Purchase #6	$225.94	13.342%	$256.0849	$256.08	$256.10	$256.10
Purchase #7	$145.90	8.516%	$158.3248	$158.32	$158.30	$158.30
7 purchase totals =	$1,007.30		$1,100.5544	$1,100.53	$1,100.45	$1,100.60