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	$206.93	7.382%	$222.2056	$222.21	$222.20	$222.20
Purchase #2	$100.58	3.338%	$103.9374	$103.94	$103.95	$103.90
Purchase #3	$205.70	6.763%	$219.6115	$219.61	$219.60	$219.60
Purchase #4	$154.26	7.270%	$165.4747	$165.47	$165.45	$165.50
Purchase #5	$100.54	3.425%	$103.9835	$103.98	$104.00	$104.00
Purchase #6	$238.35	7.706%	$256.7173	$256.72	$256.70	$256.70
Purchase #7	$242.69	3.116%	$250.2522	$250.25	$250.25	$250.30
7 purchase totals =	$1,249.05		$1,322.1822	$1,322.18	$1,322.15	$1,322.20