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	$72.45	9.332%	$79.211	$79.21	$79.20	$79.20
Purchase #2	$34.56	11.611%	$38.5728	$38.57	$38.55	$38.60
Purchase #3	$105.30	4.122%	$109.6405	$109.64	$109.65	$109.60
Purchase #4	$160.81	13.739%	$182.9037	$182.90	$182.90	$182.90
Purchase #5	$67.90	11.323%	$75.5883	$75.59	$75.60	$75.60
Purchase #6	$103.83	7.663%	$111.7865	$111.79	$111.80	$111.80
Purchase #7	$53.91	5.327%	$56.7818	$56.78	$56.80	$56.80
7 purchase totals =	$598.76		$654.4846	$654.48	$654.50	$654.50