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	$162.57	6.758%	$173.5565	$173.56	$173.55	$173.60
Purchase #2	$36.68	5.454%	$38.6805	$38.68	$38.70	$38.70
Purchase #3	$57.89	8.148%	$62.6069	$62.61	$62.60	$62.60
Purchase #4	$105.66	10.701%	$116.9667	$116.97	$116.95	$117.00
Purchase #5	$150.58	6.281%	$160.0379	$160.04	$160.05	$160.00
Purchase #6	$50.78	7.512%	$54.5946	$54.59	$54.60	$54.60
Purchase #7	$177.43	7.639%	$190.9839	$190.98	$191.00	$191.00
7 purchase totals =	$741.59		$797.4270	$797.43	$797.45	$797.50