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	$93.71	7.208%	$100.4646	$100.46	$100.45	$100.50
Purchase #2	$137.28	5.657%	$145.0459	$145.05	$145.05	$145.00
Purchase #3	$176.60	3.426%	$182.6503	$182.65	$182.65	$182.70
Purchase #4	$131.61	12.632%	$148.235	$148.24	$148.25	$148.20
Purchase #5	$207.80	9.394%	$227.3207	$227.32	$227.30	$227.30
Purchase #6	$39.46	6.693%	$42.1011	$42.10	$42.10	$42.10
Purchase #7	$160.91	8.111%	$173.9614	$173.96	$173.95	$174.00
7 purchase totals =	$947.37		$1,019.7790	$1,019.78	$1,019.75	$1,019.80