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	$31.49	4.356%	$32.8617	$32.86	$32.85	$32.90
Purchase #2	$159.71	6.205%	$169.62	$169.62	$169.60	$169.60
Purchase #3	$36.65	8.251%	$39.674	$39.67	$39.65	$39.70
Purchase #4	$87.78	13.139%	$99.3134	$99.31	$99.30	$99.30
Purchase #5	$153.42	7.211%	$164.4831	$164.48	$164.50	$164.50
Purchase #6	$143.38	7.253%	$153.7794	$153.78	$153.80	$153.80
Purchase #7	$107.97	5.800%	$114.2323	$114.23	$114.25	$114.20
7 purchase totals =	$720.40		$773.9639	$773.95	$773.95	$774.00