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	$29.43	8.577%	$31.9542	$31.95	$31.95	$32.00
Purchase #2	$188.25	11.780%	$210.4259	$210.43	$210.45	$210.40
Purchase #3	$51.27	5.815%	$54.2514	$54.25	$54.25	$54.30
Purchase #4	$84.83	5.358%	$89.3752	$89.38	$89.40	$89.40
Purchase #5	$243.89	13.815%	$277.5834	$277.58	$277.60	$277.60
Purchase #6	$121.28	5.125%	$127.4956	$127.50	$127.50	$127.50
Purchase #7	$72.61	11.675%	$81.0872	$81.09	$81.10	$81.10
7 purchase totals =	$791.56		$872.1729	$872.18	$872.25	$872.30