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	$135.38	12.295%	$152.025	$152.03	$152.05	$152.00
Purchase #2	$86.92	10.501%	$96.0475	$96.05	$96.05	$96.00
Purchase #3	$37.83	7.295%	$40.5897	$40.59	$40.60	$40.60
Purchase #4	$9.50	10.783%	$10.5244	$10.52	$10.50	$10.50
Purchase #5	$105.65	10.832%	$117.094	$117.09	$117.10	$117.10
Purchase #6	$124.96	4.762%	$130.9106	$130.91	$130.90	$130.90
Purchase #7	$182.53	5.632%	$192.8101	$192.81	$192.80	$192.80
7 purchase totals =	$682.77		$740.0013	$740.00	$740.00	$739.90