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	$73.25	7.126%	$78.4698	$78.47	$78.45	$78.50
Purchase #2	$217.39	3.814%	$225.6813	$225.68	$225.70	$225.70
Purchase #3	$44.78	9.793%	$49.1653	$49.17	$49.15	$49.20
Purchase #4	$82.33	9.626%	$90.2551	$90.26	$90.25	$90.30
Purchase #5	$179.35	7.114%	$192.109	$192.11	$192.10	$192.10
Purchase #6	$234.93	11.369%	$261.6392	$261.64	$261.65	$261.60
Purchase #7	$193.36	10.699%	$214.0476	$214.05	$214.05	$214.00
7 purchase totals =	$1,025.39		$1,111.3673	$1,111.38	$1,111.35	$1,111.40