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	$205.86	11.848%	$230.2503	$230.25	$230.25	$230.30
Purchase #2	$170.64	3.182%	$176.0698	$176.07	$176.05	$176.10
Purchase #3	$102.36	8.662%	$111.2264	$111.23	$111.25	$111.20
Purchase #4	$234.89	6.595%	$250.381	$250.38	$250.40	$250.40
Purchase #5	$141.33	3.524%	$146.3105	$146.31	$146.30	$146.30
Purchase #6	$110.78	12.348%	$124.4591	$124.46	$124.45	$124.50
Purchase #7	$25.42	6.472%	$27.0652	$27.07	$27.05	$27.10
7 purchase totals =	$991.28		$1,065.7623	$1,065.77	$1,065.75	$1,065.90