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	$83.88	4.299%	$87.486	$87.49	$87.50	$87.50
Purchase #2	$77.52	10.459%	$85.6278	$85.63	$85.65	$85.60
Purchase #3	$72.30	5.673%	$76.4016	$76.40	$76.40	$76.40
Purchase #4	$224.25	13.379%	$254.2524	$254.25	$254.25	$254.30
Purchase #5	$82.49	12.418%	$92.7336	$92.73	$92.75	$92.70
Purchase #6	$145.45	13.693%	$165.3665	$165.37	$165.35	$165.40
Purchase #7	$81.87	4.706%	$85.7228	$85.72	$85.70	$85.70
7 purchase totals =	$767.76		$847.5907	$847.59	$847.60	$847.60