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	$140.78	7.687%	$151.6018	$151.60	$151.60	$151.60
Purchase #2	$130.76	8.581%	$141.9805	$141.98	$142.00	$142.00
Purchase #3	$184.43	7.161%	$197.637	$197.64	$197.65	$197.60
Purchase #4	$57.93	12.692%	$65.2825	$65.28	$65.30	$65.30
Purchase #5	$141.38	3.570%	$146.4273	$146.43	$146.45	$146.40
Purchase #6	$118.87	7.110%	$127.3217	$127.32	$127.30	$127.30
Purchase #7	$21.63	13.853%	$24.6264	$24.63	$24.65	$24.60
7 purchase totals =	$795.78		$854.8772	$854.88	$854.95	$854.80