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	$207.56	4.683%	$217.28	$217.28	$217.30	$217.30
Purchase #2	$228.51	6.484%	$243.3266	$243.33	$243.35	$243.30
Purchase #3	$152.54	10.699%	$168.8603	$168.86	$168.85	$168.90
Purchase #4	$240.88	11.255%	$267.991	$267.99	$268.00	$268.00
Purchase #5	$17.37	4.583%	$18.1661	$18.17	$18.15	$18.20
Purchase #6	$167.61	13.725%	$190.6145	$190.61	$190.60	$190.60
Purchase #7	$208.86	9.665%	$229.0463	$229.05	$229.05	$229.00
7 purchase totals =	$1,223.33		$1,335.2848	$1,335.29	$1,335.30	$1,335.30