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	$50.44	6.276%	$53.6056	$53.61	$53.60	$53.60
Purchase #2	$18.97	8.638%	$20.6086	$20.61	$20.60	$20.60
Purchase #3	$144.47	6.694%	$154.1408	$154.14	$154.15	$154.10
Purchase #4	$163.27	6.848%	$174.4507	$174.45	$174.45	$174.50
Purchase #5	$124.84	13.381%	$141.5448	$141.54	$141.55	$141.50
Purchase #6	$228.57	7.530%	$245.7813	$245.78	$245.80	$245.80
Purchase #7	$134.94	11.293%	$150.1788	$150.18	$150.20	$150.20
7 purchase totals =	$865.50		$940.3106	$940.31	$940.35	$940.30