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	$199.85	13.866%	$227.5612	$227.56	$227.55	$227.60
Purchase #2	$11.83	5.132%	$12.4371	$12.44	$12.45	$12.40
Purchase #3	$99.41	13.229%	$112.5609	$112.56	$112.55	$112.60
Purchase #4	$75.83	6.208%	$80.5375	$80.54	$80.55	$80.50
Purchase #5	$147.82	6.326%	$157.1711	$157.17	$157.15	$157.20
Purchase #6	$76.66	13.465%	$86.9823	$86.98	$87.00	$87.00
Purchase #7	$163.74	5.363%	$172.5214	$172.52	$172.50	$172.50
7 purchase totals =	$775.14		$849.7715	$849.77	$849.75	$849.80