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	$63.72	4.813%	$66.7868	$66.79	$66.80	$66.80
Purchase #2	$89.31	12.841%	$100.7783	$100.78	$100.80	$100.80
Purchase #3	$189.30	10.312%	$208.8206	$208.82	$208.80	$208.80
Purchase #4	$217.97	9.190%	$238.0014	$238.00	$238.00	$238.00
Purchase #5	$37.51	5.201%	$39.4609	$39.46	$39.45	$39.50
Purchase #6	$44.51	13.470%	$50.5055	$50.51	$50.50	$50.50
Purchase #7	$162.46	12.863%	$183.3572	$183.36	$183.35	$183.40
7 purchase totals =	$804.78		$887.7107	$887.72	$887.70	$887.80