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	$58.90	6.295%	$62.6078	$62.61	$62.60	$62.60
Purchase #2	$160.70	11.632%	$179.3926	$179.39	$179.40	$179.40
Purchase #3	$126.27	12.702%	$142.3088	$142.31	$142.30	$142.30
Purchase #4	$124.34	10.655%	$137.5884	$137.59	$137.60	$137.60
Purchase #5	$81.56	5.662%	$86.1779	$86.18	$86.20	$86.20
Purchase #6	$244.93	13.567%	$278.1597	$278.16	$278.15	$278.20
Purchase #7	$249.80	6.426%	$265.8521	$265.85	$265.85	$265.90
7 purchase totals =	$1,046.50		$1,152.0873	$1,152.09	$1,152.10	$1,152.20