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	$225.58	6.662%	$240.6081	$240.61	$240.60	$240.60
Purchase #2	$224.64	11.253%	$249.9187	$249.92	$249.90	$249.90
Purchase #3	$88.30	4.706%	$92.4554	$92.46	$92.45	$92.50
Purchase #4	$245.37	9.292%	$268.1698	$268.17	$268.15	$268.20
Purchase #5	$51.38	5.641%	$54.2783	$54.28	$54.30	$54.30
Purchase #6	$85.53	12.254%	$96.0108	$96.01	$96.00	$96.00
Purchase #7	$134.78	12.509%	$151.6396	$151.64	$151.65	$151.60
7 purchase totals =	$1,055.58		$1,153.0807	$1,153.09	$1,153.05	$1,153.10