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	$94.34	11.646%	$105.3268	$105.33	$105.35	$105.30
Purchase #2	$60.96	7.741%	$65.6789	$65.68	$65.70	$65.70
Purchase #3	$142.37	7.195%	$152.6135	$152.61	$152.60	$152.60
Purchase #4	$247.93	3.227%	$255.9307	$255.93	$255.95	$255.90
Purchase #5	$106.66	10.209%	$117.5489	$117.55	$117.55	$117.50
Purchase #6	$131.38	11.299%	$146.2246	$146.22	$146.20	$146.20
Purchase #7	$55.74	11.348%	$62.0654	$62.07	$62.05	$62.10
7 purchase totals =	$839.38		$905.3888	$905.39	$905.40	$905.30