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	$91.92	7.562%	$98.871	$98.87	$98.85	$98.90
Purchase #2	$94.69	3.512%	$98.0155	$98.02	$98.00	$98.00
Purchase #3	$155.53	11.604%	$173.5777	$173.58	$173.60	$173.60
Purchase #4	$80.55	4.163%	$83.9033	$83.90	$83.90	$83.90
Purchase #5	$118.33	4.533%	$123.6939	$123.69	$123.70	$123.70
Purchase #6	$206.44	11.710%	$230.6141	$230.61	$230.60	$230.60
Purchase #7	$245.25	10.144%	$270.1282	$270.13	$270.15	$270.10
7 purchase totals =	$992.71		$1,078.8037	$1,078.80	$1,078.80	$1,078.80