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	$78.92	10.122%	$86.9083	$86.91	$86.90	$86.90
Purchase #2	$95.85	10.529%	$105.942	$105.94	$105.95	$105.90
Purchase #3	$214.38	4.562%	$224.16	$224.16	$224.15	$224.20
Purchase #4	$190.97	6.567%	$203.511	$203.51	$203.50	$203.50
Purchase #5	$65.58	3.517%	$67.8864	$67.89	$67.90	$67.90
Purchase #6	$126.32	12.230%	$141.7689	$141.77	$141.75	$141.80
Purchase #7	$219.59	11.856%	$245.6246	$245.62	$245.60	$245.60
7 purchase totals =	$991.61		$1,075.8012	$1,075.80	$1,075.75	$1,075.80