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	$243.33	10.478%	$268.8261	$268.83	$268.85	$268.80
Purchase #2	$139.81	9.335%	$152.8613	$152.86	$152.85	$152.90
Purchase #3	$151.98	10.649%	$168.1644	$168.16	$168.15	$168.20
Purchase #4	$239.59	10.872%	$265.6382	$265.64	$265.65	$265.60
Purchase #5	$230.30	5.191%	$242.2549	$242.25	$242.25	$242.30
Purchase #6	$103.97	8.725%	$113.0414	$113.04	$113.05	$113.00
Purchase #7	$224.88	12.769%	$253.5949	$253.59	$253.60	$253.60
7 purchase totals =	$1,333.86		$1,464.3812	$1,464.37	$1,464.40	$1,464.40