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	$86.84	10.674%	$96.1093	$96.11	$96.10	$96.10
Purchase #2	$196.75	8.832%	$214.127	$214.13	$214.15	$214.10
Purchase #3	$21.89	12.350%	$24.5934	$24.59	$24.60	$24.60
Purchase #4	$100.34	3.516%	$103.868	$103.87	$103.85	$103.90
Purchase #5	$41.89	11.748%	$46.8112	$46.81	$46.80	$46.80
Purchase #6	$152.34	12.396%	$171.2241	$171.22	$171.20	$171.20
Purchase #7	$50.25	3.367%	$51.9419	$51.94	$51.95	$51.90
7 purchase totals =	$650.30		$708.6749	$708.67	$708.65	$708.60