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	$228.93	13.444%	$259.7073	$259.71	$259.70	$259.70
Purchase #2	$219.57	11.503%	$244.8271	$244.83	$244.85	$244.80
Purchase #3	$195.57	6.788%	$208.8453	$208.85	$208.85	$208.80
Purchase #4	$195.77	7.474%	$210.4018	$210.40	$210.40	$210.40
Purchase #5	$122.28	6.730%	$130.5094	$130.51	$130.50	$130.50
Purchase #6	$25.58	6.630%	$27.276	$27.28	$27.30	$27.30
Purchase #7	$93.57	7.784%	$100.8535	$100.85	$100.85	$100.90
7 purchase totals =	$1,081.27		$1,182.4204	$1,182.43	$1,182.45	$1,182.40