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	$184.46	6.433%	$196.3263	$196.33	$196.35	$196.30
Purchase #2	$141.58	11.768%	$158.2411	$158.24	$158.25	$158.20
Purchase #3	$103.91	3.758%	$107.8149	$107.81	$107.80	$107.80
Purchase #4	$150.52	5.661%	$159.0409	$159.04	$159.05	$159.00
Purchase #5	$91.67	13.470%	$104.0179	$104.02	$104.00	$104.00
Purchase #6	$22.72	7.502%	$24.4245	$24.42	$24.40	$24.40
Purchase #7	$41.31	10.773%	$45.7603	$45.76	$45.75	$45.80
7 purchase totals =	$736.17		$795.6259	$795.62	$795.60	$795.50