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	$117.27	12.526%	$131.9592	$131.96	$131.95	$132.00
Purchase #2	$112.65	3.466%	$116.5544	$116.55	$116.55	$116.60
Purchase #3	$179.97	4.241%	$187.6025	$187.60	$187.60	$187.60
Purchase #4	$5.32	6.284%	$5.6543	$5.65	$5.65	$5.70
Purchase #5	$214.59	13.454%	$243.4609	$243.46	$243.45	$243.50
Purchase #6	$92.94	12.771%	$104.8094	$104.81	$104.80	$104.80
Purchase #7	$94.74	11.300%	$105.4456	$105.45	$105.45	$105.40
7 purchase totals =	$817.48		$895.4863	$895.48	$895.45	$895.60