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	$162.35	5.238%	$170.8539	$170.85	$170.85	$170.90
Purchase #2	$37.77	12.393%	$42.4508	$42.45	$42.45	$42.50
Purchase #3	$40.69	4.747%	$42.6216	$42.62	$42.60	$42.60
Purchase #4	$40.74	9.663%	$44.6767	$44.68	$44.70	$44.70
Purchase #5	$205.41	6.377%	$218.509	$218.51	$218.50	$218.50
Purchase #6	$42.98	4.420%	$44.8797	$44.88	$44.90	$44.90
Purchase #7	$95.71	5.501%	$100.975	$100.98	$101.00	$101.00
7 purchase totals =	$625.65		$664.9667	$664.97	$665.00	$665.10