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	$30.63	8.768%	$33.3156	$33.32	$33.30	$33.30
Purchase #2	$60.87	6.738%	$64.9714	$64.97	$64.95	$65.00
Purchase #3	$241.25	10.679%	$267.0131	$267.01	$267.00	$267.00
Purchase #4	$71.75	9.112%	$78.2879	$78.29	$78.30	$78.30
Purchase #5	$5.62	8.458%	$6.0953	$6.10	$6.10	$6.10
Purchase #6	$97.56	11.310%	$108.594	$108.59	$108.60	$108.60
Purchase #7	$121.71	4.827%	$127.5849	$127.58	$127.60	$127.60
7 purchase totals =	$629.39		$685.8622	$685.86	$685.85	$685.90