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	$156.77	7.561%	$168.6234	$168.62	$168.60	$168.60
Purchase #2	$78.62	5.534%	$82.9708	$82.97	$82.95	$83.00
Purchase #3	$158.93	12.257%	$178.4101	$178.41	$178.40	$178.40
Purchase #4	$151.43	4.505%	$158.2519	$158.25	$158.25	$158.30
Purchase #5	$161.59	3.647%	$167.4832	$167.48	$167.50	$167.50
Purchase #6	$51.64	7.345%	$55.433	$55.43	$55.45	$55.40
Purchase #7	$39.73	5.287%	$41.8305	$41.83	$41.85	$41.80
7 purchase totals =	$798.71		$853.0029	$852.99	$853.00	$853.00