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	$155.25	7.845%	$167.4294	$167.43	$167.45	$167.40
Purchase #2	$184.97	13.591%	$210.1093	$210.11	$210.10	$210.10
Purchase #3	$131.62	10.529%	$145.4783	$145.48	$145.50	$145.50
Purchase #4	$44.44	4.635%	$46.4998	$46.50	$46.50	$46.50
Purchase #5	$66.58	5.366%	$70.1527	$70.15	$70.15	$70.20
Purchase #6	$213.37	4.239%	$222.4148	$222.41	$222.40	$222.40
Purchase #7	$57.80	4.688%	$60.5097	$60.51	$60.50	$60.50
7 purchase totals =	$854.03		$922.5940	$922.59	$922.60	$922.60