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	$234.84	9.840%	$257.9483	$257.95	$257.95	$257.90
Purchase #2	$48.38	10.617%	$53.5165	$53.52	$53.50	$53.50
Purchase #3	$167.69	12.662%	$188.9229	$188.92	$188.90	$188.90
Purchase #4	$160.56	9.853%	$176.38	$176.38	$176.40	$176.40
Purchase #5	$170.92	13.507%	$194.0062	$194.01	$194.00	$194.00
Purchase #6	$117.60	8.762%	$127.9041	$127.90	$127.90	$127.90
Purchase #7	$29.46	10.524%	$32.5604	$32.56	$32.55	$32.60
7 purchase totals =	$929.45		$1,031.2384	$1,031.24	$1,031.20	$1,031.20