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	$91.76	13.373%	$104.0311	$104.03	$104.05	$104.00
Purchase #2	$77.31	12.440%	$86.9274	$86.93	$86.95	$86.90
Purchase #3	$120.27	9.847%	$132.113	$132.11	$132.10	$132.10
Purchase #4	$234.80	5.769%	$248.3456	$248.35	$248.35	$248.30
Purchase #5	$55.28	10.212%	$60.9252	$60.93	$60.95	$60.90
Purchase #6	$19.66	4.116%	$20.4692	$20.47	$20.45	$20.50
Purchase #7	$176.69	11.259%	$196.5835	$196.58	$196.60	$196.60
7 purchase totals =	$775.77		$849.3950	$849.40	$849.45	$849.30