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	$82.54	3.811%	$85.6856	$85.69	$85.70	$85.70
Purchase #2	$52.59	8.486%	$57.0528	$57.05	$57.05	$57.10
Purchase #3	$128.77	12.413%	$144.7542	$144.75	$144.75	$144.80
Purchase #4	$123.57	10.772%	$136.881	$136.88	$136.90	$136.90
Purchase #5	$177.28	5.104%	$186.3284	$186.33	$186.35	$186.30
Purchase #6	$66.41	7.241%	$71.2187	$71.22	$71.20	$71.20
Purchase #7	$163.97	10.680%	$181.482	$181.48	$181.50	$181.50
7 purchase totals =	$795.13		$863.4027	$863.40	$863.45	$863.50