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	$85.32	10.209%	$94.0303	$94.03	$94.05	$94.00
Purchase #2	$82.48	3.545%	$85.4039	$85.40	$85.40	$85.40
Purchase #3	$92.77	8.806%	$100.9393	$100.94	$100.95	$100.90
Purchase #4	$186.29	5.212%	$195.9994	$196.00	$196.00	$196.00
Purchase #5	$65.72	9.422%	$71.9121	$71.91	$71.90	$71.90
Purchase #6	$172.85	8.275%	$187.1533	$187.15	$187.15	$187.20
Purchase #7	$85.51	11.794%	$95.595	$95.60	$95.60	$95.60
7 purchase totals =	$770.94		$831.0333	$831.03	$831.05	$831.00