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	$176.57	13.826%	$200.9826	$200.98	$201.00	$201.00
Purchase #2	$82.39	10.361%	$90.9264	$90.93	$90.95	$90.90
Purchase #3	$102.46	13.650%	$116.4458	$116.45	$116.45	$116.40
Purchase #4	$249.91	3.495%	$258.6444	$258.64	$258.65	$258.60
Purchase #5	$100.57	11.448%	$112.0833	$112.08	$112.10	$112.10
Purchase #6	$208.50	8.117%	$225.4239	$225.42	$225.40	$225.40
Purchase #7	$248.96	10.635%	$275.4369	$275.44	$275.45	$275.40
7 purchase totals =	$1,169.36		$1,279.9433	$1,279.94	$1,280.00	$1,279.80