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	$87.29	10.696%	$96.6265	$96.63	$96.65	$96.60
Purchase #2	$209.94	8.549%	$227.8878	$227.89	$227.90	$227.90
Purchase #3	$225.55	5.732%	$238.4785	$238.48	$238.50	$238.50
Purchase #4	$68.85	13.621%	$78.2281	$78.23	$78.25	$78.20
Purchase #5	$230.52	8.728%	$250.6398	$250.64	$250.65	$250.60
Purchase #6	$226.51	12.391%	$254.5769	$254.58	$254.60	$254.60
Purchase #7	$100.42	12.696%	$113.1693	$113.17	$113.15	$113.20
7 purchase totals =	$1,149.08		$1,259.6069	$1,259.62	$1,259.70	$1,259.60