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	$119.37	11.233%	$132.7788	$132.78	$132.80	$132.80
Purchase #2	$211.44	6.184%	$224.5154	$224.52	$224.50	$224.50
Purchase #3	$136.57	11.401%	$152.1403	$152.14	$152.15	$152.10
Purchase #4	$40.44	9.296%	$44.1993	$44.20	$44.20	$44.20
Purchase #5	$33.36	3.694%	$34.5923	$34.59	$34.60	$34.60
Purchase #6	$115.32	11.468%	$128.5449	$128.54	$128.55	$128.50
Purchase #7	$72.82	9.671%	$79.8624	$79.86	$79.85	$79.90
7 purchase totals =	$729.32		$796.6334	$796.63	$796.65	$796.60