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	$20.36	11.725%	$22.7472	$22.75	$22.75	$22.70
Purchase #2	$27.51	5.116%	$28.9174	$28.92	$28.90	$28.90
Purchase #3	$70.38	11.467%	$78.4505	$78.45	$78.45	$78.50
Purchase #4	$60.95	12.172%	$68.3688	$68.37	$68.35	$68.40
Purchase #5	$28.44	13.110%	$32.1685	$32.17	$32.15	$32.20
Purchase #6	$212.46	12.140%	$238.2526	$238.25	$238.25	$238.30
Purchase #7	$37.47	3.671%	$38.8455	$38.85	$38.85	$38.80
7 purchase totals =	$457.57		$507.7505	$507.76	$507.70	$507.80