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	$142.79	5.423%	$150.5335	$150.53	$150.55	$150.50
Purchase #2	$126.45	3.356%	$130.6937	$130.69	$130.70	$130.70
Purchase #3	$132.81	10.372%	$146.5851	$146.59	$146.60	$146.60
Purchase #4	$100.76	11.127%	$111.9716	$111.97	$111.95	$112.00
Purchase #5	$65.84	3.163%	$67.9225	$67.92	$67.90	$67.90
Purchase #6	$85.40	10.190%	$94.1023	$94.10	$94.10	$94.10
Purchase #7	$11.55	3.459%	$11.9495	$11.95	$11.95	$11.90
7 purchase totals =	$665.60		$713.7582	$713.75	$713.75	$713.70