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	$198.93	9.151%	$217.1341	$217.13	$217.15	$217.10
Purchase #2	$22.60	4.453%	$23.6064	$23.61	$23.60	$23.60
Purchase #3	$87.83	13.641%	$99.8109	$99.81	$99.80	$99.80
Purchase #4	$6.99	6.362%	$7.4347	$7.43	$7.45	$7.40
Purchase #5	$120.70	5.304%	$127.1019	$127.10	$127.10	$127.10
Purchase #6	$51.58	9.346%	$56.4007	$56.40	$56.40	$56.40
Purchase #7	$131.77	10.164%	$145.1631	$145.16	$145.15	$145.20
7 purchase totals =	$620.40		$676.6518	$676.64	$676.65	$676.60