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	$215.27	4.680%	$225.3446	$225.34	$225.35	$225.30
Purchase #2	$36.86	3.236%	$38.0528	$38.05	$38.05	$38.10
Purchase #3	$248.66	12.182%	$278.9518	$278.95	$278.95	$279.00
Purchase #4	$84.56	11.863%	$94.5914	$94.59	$94.60	$94.60
Purchase #5	$188.59	4.195%	$196.5014	$196.50	$196.50	$196.50
Purchase #6	$182.36	10.164%	$200.8951	$200.90	$200.90	$200.90
Purchase #7	$243.39	5.491%	$256.7545	$256.75	$256.75	$256.80
7 purchase totals =	$1,199.69		$1,291.0916	$1,291.08	$1,291.10	$1,291.20