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	$164.74	7.339%	$176.8303	$176.83	$176.85	$176.80
Purchase #2	$176.78	3.780%	$183.4623	$183.46	$183.45	$183.50
Purchase #3	$162.86	5.312%	$171.5111	$171.51	$171.50	$171.50
Purchase #4	$17.42	7.816%	$18.7815	$18.78	$18.80	$18.80
Purchase #5	$165.95	8.701%	$180.3893	$180.39	$180.40	$180.40
Purchase #6	$18.43	5.584%	$19.4591	$19.46	$19.45	$19.50
Purchase #7	$130.73	10.170%	$144.0252	$144.03	$144.05	$144.00
7 purchase totals =	$836.91		$894.4588	$894.46	$894.50	$894.50