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	$174.29	13.654%	$198.0876	$198.09	$198.10	$198.10
Purchase #2	$14.78	5.436%	$15.5834	$15.58	$15.60	$15.60
Purchase #3	$168.83	5.493%	$178.1038	$178.10	$178.10	$178.10
Purchase #4	$156.54	7.210%	$167.8265	$167.83	$167.85	$167.80
Purchase #5	$69.66	4.692%	$72.9284	$72.93	$72.95	$72.90
Purchase #6	$117.63	8.319%	$127.4156	$127.42	$127.40	$127.40
Purchase #7	$212.79	10.140%	$234.3669	$234.37	$234.35	$234.40
7 purchase totals =	$914.52		$994.3122	$994.32	$994.35	$994.30