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	$84.44	6.156%	$89.6381	$89.64	$89.65	$89.60
Purchase #2	$105.32	13.845%	$119.9016	$119.90	$119.90	$119.90
Purchase #3	$141.44	3.613%	$146.5502	$146.55	$146.55	$146.60
Purchase #4	$218.85	5.465%	$230.8102	$230.81	$230.80	$230.80
Purchase #5	$81.98	8.382%	$88.8516	$88.85	$88.85	$88.90
Purchase #6	$190.91	4.611%	$199.7129	$199.71	$199.70	$199.70
Purchase #7	$216.50	6.393%	$230.3408	$230.34	$230.35	$230.30
7 purchase totals =	$1,039.44		$1,105.8054	$1,105.80	$1,105.80	$1,105.80