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	$178.27	5.412%	$187.918	$187.92	$187.90	$187.90
Purchase #2	$90.57	5.835%	$95.8548	$95.85	$95.85	$95.90
Purchase #3	$176.38	10.309%	$194.563	$194.56	$194.55	$194.60
Purchase #4	$17.66	12.386%	$19.8474	$19.85	$19.85	$19.80
Purchase #5	$123.60	5.483%	$130.377	$130.38	$130.40	$130.40
Purchase #6	$75.78	12.809%	$85.4867	$85.49	$85.50	$85.50
Purchase #7	$114.51	13.560%	$130.0376	$130.04	$130.05	$130.00
7 purchase totals =	$776.77		$844.0845	$844.09	$844.10	$844.10