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	$242.30	12.595%	$272.8177	$272.82	$272.80	$272.80
Purchase #2	$45.33	3.254%	$46.805	$46.81	$46.80	$46.80
Purchase #3	$179.47	9.423%	$196.3815	$196.38	$196.40	$196.40
Purchase #4	$152.64	13.324%	$172.9778	$172.98	$173.00	$173.00
Purchase #5	$228.84	7.133%	$245.1632	$245.16	$245.15	$245.20
Purchase #6	$13.59	4.217%	$14.1631	$14.16	$14.15	$14.20
Purchase #7	$64.60	9.260%	$70.582	$70.58	$70.60	$70.60
7 purchase totals =	$926.77		$1,018.8903	$1,018.89	$1,018.90	$1,019.00