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	$221.98	3.655%	$230.0934	$230.09	$230.10	$230.10
Purchase #2	$7.29	3.268%	$7.5282	$7.53	$7.55	$7.50
Purchase #3	$93.88	10.295%	$103.5449	$103.54	$103.55	$103.50
Purchase #4	$104.47	13.407%	$118.4763	$118.48	$118.50	$118.50
Purchase #5	$82.95	9.424%	$90.7672	$90.77	$90.75	$90.80
Purchase #6	$33.70	3.823%	$34.9884	$34.99	$35.00	$35.00
Purchase #7	$228.43	13.176%	$258.5279	$258.53	$258.55	$258.50
7 purchase totals =	$772.70		$843.9263	$843.93	$844.00	$843.90