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	$196.25	4.668%	$205.411	$205.41	$205.40	$205.40
Purchase #2	$91.60	13.645%	$104.0988	$104.10	$104.10	$104.10
Purchase #3	$34.77	13.396%	$39.4278	$39.43	$39.45	$39.40
Purchase #4	$225.85	3.246%	$233.1811	$233.18	$233.20	$233.20
Purchase #5	$25.32	8.659%	$27.5125	$27.51	$27.50	$27.50
Purchase #6	$31.25	3.263%	$32.2697	$32.27	$32.25	$32.30
Purchase #7	$49.62	11.545%	$55.3486	$55.35	$55.35	$55.30
7 purchase totals =	$654.66		$697.2495	$697.25	$697.25	$697.20