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	$183.88	13.335%	$208.4004	$208.40	$208.40	$208.40
Purchase #2	$221.41	9.488%	$242.4174	$242.42	$242.40	$242.40
Purchase #3	$188.89	5.677%	$199.6133	$199.61	$199.60	$199.60
Purchase #4	$39.41	12.490%	$44.3323	$44.33	$44.35	$44.30
Purchase #5	$153.76	6.721%	$164.0942	$164.09	$164.10	$164.10
Purchase #6	$140.47	4.565%	$146.8825	$146.88	$146.90	$146.90
Purchase #7	$92.60	13.553%	$105.1501	$105.15	$105.15	$105.20
7 purchase totals =	$1,020.42		$1,110.8902	$1,110.88	$1,110.90	$1,110.90