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	$132.38	10.786%	$146.6585	$146.66	$146.65	$146.70
Purchase #2	$124.51	13.739%	$141.6164	$141.62	$141.60	$141.60
Purchase #3	$92.62	4.629%	$96.9074	$96.91	$96.90	$96.90
Purchase #4	$245.97	4.777%	$257.72	$257.72	$257.70	$257.70
Purchase #5	$189.50	3.571%	$196.267	$196.27	$196.25	$196.30
Purchase #6	$248.81	3.141%	$256.6251	$256.63	$256.65	$256.60
Purchase #7	$102.42	13.801%	$116.555	$116.56	$116.55	$116.60
7 purchase totals =	$1,136.21		$1,212.3494	$1,212.37	$1,212.30	$1,212.40