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	$161.55	4.600%	$168.9813	$168.98	$169.00	$169.00
Purchase #2	$171.95	5.180%	$180.857	$180.86	$180.85	$180.90
Purchase #3	$106.79	5.105%	$112.2416	$112.24	$112.25	$112.20
Purchase #4	$155.35	7.699%	$167.3104	$167.31	$167.30	$167.30
Purchase #5	$12.83	8.268%	$13.8908	$13.89	$13.90	$13.90
Purchase #6	$156.96	5.653%	$165.8329	$165.83	$165.85	$165.80
Purchase #7	$222.49	11.545%	$248.1765	$248.18	$248.20	$248.20
7 purchase totals =	$987.92		$1,057.2905	$1,057.29	$1,057.35	$1,057.30