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	$159.87	7.768%	$172.2887	$172.29	$172.30	$172.30
Purchase #2	$35.69	7.657%	$38.4228	$38.42	$38.40	$38.40
Purchase #3	$25.28	10.159%	$27.8482	$27.85	$27.85	$27.80
Purchase #4	$30.85	5.355%	$32.502	$32.50	$32.50	$32.50
Purchase #5	$244.51	5.450%	$257.8358	$257.84	$257.85	$257.80
Purchase #6	$101.78	10.625%	$112.5941	$112.59	$112.60	$112.60
Purchase #7	$208.44	12.471%	$234.4346	$234.43	$234.45	$234.40
7 purchase totals =	$806.42		$875.9262	$875.92	$875.95	$875.80