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	$57.97	5.255%	$61.0163	$61.02	$61.00	$61.00
Purchase #2	$77.51	11.720%	$86.5942	$86.59	$86.60	$86.60
Purchase #3	$102.98	8.582%	$111.8177	$111.82	$111.80	$111.80
Purchase #4	$224.79	11.398%	$250.4116	$250.41	$250.40	$250.40
Purchase #5	$178.97	10.604%	$197.948	$197.95	$197.95	$197.90
Purchase #6	$104.75	6.138%	$111.1796	$111.18	$111.20	$111.20
Purchase #7	$128.86	6.711%	$137.5078	$137.51	$137.50	$137.50
7 purchase totals =	$875.83		$956.4752	$956.48	$956.45	$956.40