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	$68.53	5.420%	$72.2443	$72.24	$72.25	$72.20
Purchase #2	$205.85	5.423%	$217.0132	$217.01	$217.00	$217.00
Purchase #3	$198.61	9.672%	$217.8196	$217.82	$217.80	$217.80
Purchase #4	$5.96	7.144%	$6.3858	$6.39	$6.40	$6.40
Purchase #5	$55.78	11.793%	$62.3581	$62.36	$62.35	$62.40
Purchase #6	$139.30	13.540%	$158.1612	$158.16	$158.15	$158.20
Purchase #7	$47.26	6.789%	$50.4685	$50.47	$50.45	$50.50
7 purchase totals =	$721.29		$784.4507	$784.45	$784.40	$784.50