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	$82.48	10.163%	$90.8624	$90.86	$90.85	$90.90
Purchase #2	$10.60	8.329%	$11.4829	$11.48	$11.50	$11.50
Purchase #3	$233.90	11.727%	$261.3295	$261.33	$261.35	$261.30
Purchase #4	$154.51	6.478%	$164.5192	$164.52	$164.50	$164.50
Purchase #5	$53.68	7.725%	$57.8268	$57.83	$57.85	$57.80
Purchase #6	$180.25	4.390%	$188.163	$188.16	$188.15	$188.20
Purchase #7	$96.86	9.459%	$106.022	$106.02	$106.00	$106.00
7 purchase totals =	$812.28		$880.2058	$880.20	$880.20	$880.20