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	$160.65	6.775%	$171.534	$171.53	$171.55	$171.50
Purchase #2	$153.85	7.808%	$165.8626	$165.86	$165.85	$165.90
Purchase #3	$167.76	3.479%	$173.5964	$173.60	$173.60	$173.60
Purchase #4	$228.42	11.571%	$254.8505	$254.85	$254.85	$254.90
Purchase #5	$105.86	11.859%	$118.4139	$118.41	$118.40	$118.40
Purchase #6	$8.55	4.393%	$8.9256	$8.93	$8.95	$8.90
Purchase #7	$64.76	11.717%	$72.3479	$72.35	$72.35	$72.30
7 purchase totals =	$889.85		$965.5309	$965.53	$965.55	$965.50