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	$222.43	11.446%	$247.8893	$247.89	$247.90	$247.90
Purchase #2	$186.82	9.739%	$205.0144	$205.01	$205.00	$205.00
Purchase #3	$144.80	13.839%	$164.8389	$164.84	$164.85	$164.80
Purchase #4	$103.81	8.803%	$112.9484	$112.95	$112.95	$112.90
Purchase #5	$206.48	10.635%	$228.4391	$228.44	$228.45	$228.40
Purchase #6	$248.54	10.503%	$274.6442	$274.64	$274.65	$274.60
Purchase #7	$223.89	13.278%	$253.6181	$253.62	$253.60	$253.60
7 purchase totals =	$1,336.77		$1,487.3924	$1,487.39	$1,487.40	$1,487.20