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	$10.43	9.770%	$11.449	$11.45	$11.45	$11.40
Purchase #2	$134.68	5.716%	$142.3783	$142.38	$142.40	$142.40
Purchase #3	$227.78	8.430%	$246.9819	$246.98	$247.00	$247.00
Purchase #4	$64.33	12.110%	$72.1204	$72.12	$72.10	$72.10
Purchase #5	$223.34	8.433%	$242.1743	$242.17	$242.15	$242.20
Purchase #6	$154.29	5.336%	$162.5229	$162.52	$162.50	$162.50
Purchase #7	$125.25	12.587%	$141.0152	$141.02	$141.00	$141.00
7 purchase totals =	$940.10		$1,018.6420	$1,018.64	$1,018.60	$1,018.60