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	$32.89	6.775%	$35.1183	$35.12	$35.10	$35.10
Purchase #2	$86.37	4.523%	$90.2765	$90.28	$90.30	$90.30
Purchase #3	$45.58	13.340%	$51.6604	$51.66	$51.65	$51.70
Purchase #4	$161.34	10.667%	$178.5501	$178.55	$178.55	$178.60
Purchase #5	$56.49	10.491%	$62.4164	$62.42	$62.40	$62.40
Purchase #6	$30.64	7.214%	$32.8504	$32.85	$32.85	$32.90
Purchase #7	$7.35	5.340%	$7.7425	$7.74	$7.75	$7.70
7 purchase totals =	$420.66		$458.6146	$458.62	$458.60	$458.70