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	$193.86	8.400%	$210.1442	$210.14	$210.15	$210.10
Purchase #2	$95.52	4.473%	$99.7926	$99.79	$99.80	$99.80
Purchase #3	$104.78	11.829%	$117.1744	$117.17	$117.15	$117.20
Purchase #4	$87.79	13.720%	$99.8348	$99.83	$99.85	$99.80
Purchase #5	$248.92	3.817%	$258.4213	$258.42	$258.40	$258.40
Purchase #6	$59.99	6.840%	$64.0933	$64.09	$64.10	$64.10
Purchase #7	$208.82	9.264%	$228.1651	$228.17	$228.15	$228.20
7 purchase totals =	$999.68		$1,077.6257	$1,077.61	$1,077.60	$1,077.60