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	$32.88	4.820%	$34.4648	$34.46	$34.45	$34.50
Purchase #2	$225.58	12.329%	$253.3918	$253.39	$253.40	$253.40
Purchase #3	$222.73	4.812%	$233.4478	$233.45	$233.45	$233.40
Purchase #4	$43.25	3.144%	$44.6098	$44.61	$44.60	$44.60
Purchase #5	$96.28	10.657%	$106.5406	$106.54	$106.55	$106.50
Purchase #6	$148.83	3.379%	$153.859	$153.86	$153.85	$153.90
Purchase #7	$99.92	10.670%	$110.5815	$110.58	$110.60	$110.60
7 purchase totals =	$869.47		$936.8953	$936.89	$936.90	$936.90