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	$205.48	5.816%	$217.4307	$217.43	$217.45	$217.40
Purchase #2	$48.88	5.534%	$51.585	$51.59	$51.60	$51.60
Purchase #3	$19.25	3.521%	$19.9278	$19.93	$19.95	$19.90
Purchase #4	$137.98	12.782%	$155.6166	$155.62	$155.60	$155.60
Purchase #5	$137.66	9.608%	$150.8864	$150.89	$150.90	$150.90
Purchase #6	$78.60	3.169%	$81.0908	$81.09	$81.10	$81.10
Purchase #7	$131.75	11.243%	$146.5627	$146.56	$146.55	$146.60
7 purchase totals =	$759.60		$823.1000	$823.11	$823.15	$823.10