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	$82.62	10.848%	$91.5826	$91.58	$91.60	$91.60
Purchase #2	$125.61	4.748%	$131.574	$131.57	$131.55	$131.60
Purchase #3	$45.60	9.480%	$49.9229	$49.92	$49.90	$49.90
Purchase #4	$42.87	7.334%	$46.0141	$46.01	$46.00	$46.00
Purchase #5	$176.42	5.586%	$186.2748	$186.27	$186.25	$186.30
Purchase #6	$160.40	6.553%	$170.911	$170.91	$170.90	$170.90
Purchase #7	$120.77	3.425%	$124.9064	$124.91	$124.90	$124.90
7 purchase totals =	$754.29		$801.1858	$801.17	$801.10	$801.20