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	$92.85	11.438%	$103.4702	$103.47	$103.45	$103.50
Purchase #2	$86.83	4.745%	$90.9501	$90.95	$90.95	$91.00
Purchase #3	$44.50	10.351%	$49.1062	$49.11	$49.10	$49.10
Purchase #4	$96.83	13.357%	$109.7636	$109.76	$109.75	$109.80
Purchase #5	$85.69	6.152%	$90.9616	$90.96	$90.95	$91.00
Purchase #6	$205.42	9.431%	$224.7932	$224.79	$224.80	$224.80
Purchase #7	$134.41	8.196%	$145.4262	$145.43	$145.45	$145.40
7 purchase totals =	$746.53		$814.4711	$814.47	$814.45	$814.60