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	$42.32	5.394%	$44.6027	$44.60	$44.60	$44.60
Purchase #2	$241.26	4.589%	$252.3314	$252.33	$252.35	$252.30
Purchase #3	$183.32	3.421%	$189.5914	$189.59	$189.60	$189.60
Purchase #4	$108.77	4.299%	$113.446	$113.45	$113.45	$113.40
Purchase #5	$226.38	13.352%	$256.6063	$256.61	$256.60	$256.60
Purchase #6	$172.78	13.623%	$196.3178	$196.32	$196.30	$196.30
Purchase #7	$185.47	3.620%	$192.184	$192.18	$192.20	$192.20
7 purchase totals =	$1,160.30		$1,245.0796	$1,245.08	$1,245.10	$1,245.00