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	$58.55	9.745%	$64.2557	$64.26	$64.25	$64.30
Purchase #2	$224.78	12.857%	$253.68	$253.68	$253.70	$253.70
Purchase #3	$229.42	11.302%	$255.349	$255.35	$255.35	$255.30
Purchase #4	$85.60	4.866%	$89.7653	$89.77	$89.75	$89.80
Purchase #5	$29.78	12.746%	$33.5758	$33.58	$33.60	$33.60
Purchase #6	$156.41	3.518%	$161.9125	$161.91	$161.90	$161.90
Purchase #7	$119.62	6.600%	$127.5149	$127.51	$127.50	$127.50
7 purchase totals =	$904.16		$986.0532	$986.06	$986.05	$986.10