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	$236.56	8.826%	$257.4388	$257.44	$257.45	$257.40
Purchase #2	$203.62	13.531%	$231.1718	$231.17	$231.15	$231.20
Purchase #3	$108.40	9.329%	$118.5126	$118.51	$118.50	$118.50
Purchase #4	$131.83	11.372%	$146.8217	$146.82	$146.80	$146.80
Purchase #5	$188.79	4.280%	$196.8702	$196.87	$196.85	$196.90
Purchase #6	$40.56	3.287%	$41.8932	$41.89	$41.90	$41.90
Purchase #7	$153.68	9.389%	$168.109	$168.11	$168.10	$168.10
7 purchase totals =	$1,063.44		$1,160.8173	$1,160.81	$1,160.75	$1,160.80