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	$96.72	11.645%	$107.983	$107.98	$108.00	$108.00
Purchase #2	$220.48	9.573%	$241.5866	$241.59	$241.60	$241.60
Purchase #3	$124.91	12.761%	$140.8498	$140.85	$140.85	$140.80
Purchase #4	$153.89	12.655%	$173.3648	$173.36	$173.35	$173.40
Purchase #5	$116.66	13.340%	$132.2224	$132.22	$132.20	$132.20
Purchase #6	$74.80	7.331%	$80.2836	$80.28	$80.30	$80.30
Purchase #7	$228.41	11.758%	$255.2664	$255.27	$255.25	$255.30
7 purchase totals =	$1,015.87		$1,131.5566	$1,131.55	$1,131.55	$1,131.60