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	$85.78	11.176%	$95.3668	$95.37	$95.35	$95.40
Purchase #2	$236.27	9.255%	$258.1368	$258.14	$258.15	$258.10
Purchase #3	$145.82	6.303%	$155.011	$155.01	$155.00	$155.00
Purchase #4	$242.91	3.650%	$251.7762	$251.78	$251.80	$251.80
Purchase #5	$159.90	8.152%	$172.935	$172.94	$172.95	$172.90
Purchase #6	$111.59	4.542%	$116.6584	$116.66	$116.65	$116.70
Purchase #7	$113.37	3.191%	$116.9876	$116.99	$117.00	$117.00
7 purchase totals =	$1,095.64		$1,166.8718	$1,166.89	$1,166.90	$1,166.90