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	$103.28	6.725%	$110.2256	$110.23	$110.25	$110.20
Purchase #2	$167.80	8.737%	$182.4607	$182.46	$182.45	$182.50
Purchase #3	$238.43	6.678%	$254.3524	$254.35	$254.35	$254.40
Purchase #4	$205.56	8.310%	$222.642	$222.64	$222.65	$222.60
Purchase #5	$207.68	4.338%	$216.6892	$216.69	$216.70	$216.70
Purchase #6	$67.53	5.757%	$71.4177	$71.42	$71.40	$71.40
Purchase #7	$35.60	11.792%	$39.798	$39.80	$39.80	$39.80
7 purchase totals =	$1,025.88		$1,097.5856	$1,097.59	$1,097.60	$1,097.60