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	$105.82	10.339%	$116.7607	$116.76	$116.75	$116.80
Purchase #2	$131.75	8.224%	$142.5851	$142.59	$142.60	$142.60
Purchase #3	$201.33	13.320%	$228.1472	$228.15	$228.15	$228.10
Purchase #4	$226.79	6.690%	$241.9623	$241.96	$241.95	$242.00
Purchase #5	$158.60	12.469%	$178.3758	$178.38	$178.40	$178.40
Purchase #6	$98.46	3.458%	$101.8647	$101.86	$101.85	$101.90
Purchase #7	$123.70	10.365%	$136.5215	$136.52	$136.50	$136.50
7 purchase totals =	$1,046.45		$1,146.2173	$1,146.22	$1,146.20	$1,146.30