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	$90.47	7.181%	$96.9667	$96.97	$96.95	$97.00
Purchase #2	$166.25	10.789%	$184.1867	$184.19	$184.20	$184.20
Purchase #3	$57.72	9.417%	$63.1555	$63.16	$63.15	$63.20
Purchase #4	$244.43	8.198%	$264.4684	$264.47	$264.45	$264.50
Purchase #5	$82.36	9.853%	$90.4749	$90.47	$90.45	$90.50
Purchase #6	$171.63	9.483%	$187.9057	$187.91	$187.90	$187.90
Purchase #7	$178.92	6.705%	$190.9166	$190.92	$190.90	$190.90
7 purchase totals =	$991.78		$1,078.0745	$1,078.09	$1,078.00	$1,078.20