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	$159.54	8.487%	$173.0802	$173.08	$173.10	$173.10
Purchase #2	$39.35	5.669%	$41.5808	$41.58	$41.60	$41.60
Purchase #3	$233.80	6.421%	$248.8123	$248.81	$248.80	$248.80
Purchase #4	$19.92	7.273%	$21.3688	$21.37	$21.35	$21.40
Purchase #5	$178.87	4.322%	$186.6008	$186.60	$186.60	$186.60
Purchase #6	$37.60	8.787%	$40.9039	$40.90	$40.90	$40.90
Purchase #7	$37.66	12.449%	$42.3483	$42.35	$42.35	$42.30
7 purchase totals =	$706.74		$754.6951	$754.69	$754.70	$754.70