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	$92.78	11.454%	$103.407	$103.41	$103.40	$103.40
Purchase #2	$227.89	8.432%	$247.1057	$247.11	$247.10	$247.10
Purchase #3	$222.83	11.488%	$248.4287	$248.43	$248.45	$248.40
Purchase #4	$187.89	13.858%	$213.9278	$213.93	$213.95	$213.90
Purchase #5	$111.66	10.673%	$123.5775	$123.58	$123.60	$123.60
Purchase #6	$24.62	11.573%	$27.4693	$27.47	$27.45	$27.50
Purchase #7	$61.83	10.318%	$68.2096	$68.21	$68.20	$68.20
7 purchase totals =	$929.50		$1,032.1256	$1,032.14	$1,032.15	$1,032.10