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	$89.40	10.282%	$98.5921	$98.59	$98.60	$98.60
Purchase #2	$225.42	3.381%	$233.0415	$233.04	$233.05	$233.00
Purchase #3	$34.49	12.762%	$38.8916	$38.89	$38.90	$38.90
Purchase #4	$90.35	8.459%	$97.9927	$97.99	$98.00	$98.00
Purchase #5	$201.37	10.861%	$223.2408	$223.24	$223.25	$223.20
Purchase #6	$225.25	5.105%	$236.749	$236.75	$236.75	$236.70
Purchase #7	$166.70	3.459%	$172.4662	$172.47	$172.45	$172.50
7 purchase totals =	$1,032.98		$1,100.9739	$1,100.97	$1,101.00	$1,100.90