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	$101.51	4.336%	$105.9115	$105.91	$105.90	$105.90
Purchase #2	$183.36	10.446%	$202.5138	$202.51	$202.50	$202.50
Purchase #3	$108.27	13.693%	$123.0954	$123.10	$123.10	$123.10
Purchase #4	$49.71	8.262%	$53.817	$53.82	$53.80	$53.80
Purchase #5	$69.48	6.244%	$73.8183	$73.82	$73.80	$73.80
Purchase #6	$227.64	4.223%	$237.2532	$237.25	$237.25	$237.30
Purchase #7	$141.25	7.264%	$151.5104	$151.51	$151.50	$151.50
7 purchase totals =	$881.22		$947.9196	$947.92	$947.85	$947.90