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	$92.61	8.454%	$100.4392	$100.44	$100.45	$100.40
Purchase #2	$167.67	11.815%	$187.4802	$187.48	$187.50	$187.50
Purchase #3	$10.64	10.391%	$11.7456	$11.75	$11.75	$11.70
Purchase #4	$61.52	9.523%	$67.3785	$67.38	$67.40	$67.40
Purchase #5	$81.36	11.173%	$90.4504	$90.45	$90.45	$90.50
Purchase #6	$139.87	8.745%	$152.1016	$152.10	$152.10	$152.10
Purchase #7	$7.83	11.357%	$8.7193	$8.72	$8.70	$8.70
7 purchase totals =	$561.50		$618.3148	$618.32	$618.35	$618.30