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	$162.86	3.434%	$168.4526	$168.45	$168.45	$168.50
Purchase #2	$12.86	6.391%	$13.6819	$13.68	$13.70	$13.70
Purchase #3	$128.28	10.779%	$142.1073	$142.11	$142.10	$142.10
Purchase #4	$84.64	6.526%	$90.1636	$90.16	$90.15	$90.20
Purchase #5	$98.66	13.582%	$112.06	$112.06	$112.05	$112.10
Purchase #6	$117.49	4.508%	$122.7864	$122.79	$122.80	$122.80
Purchase #7	$183.50	3.600%	$190.106	$190.11	$190.10	$190.10
7 purchase totals =	$788.29		$839.3578	$839.36	$839.35	$839.50