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	$133.44	4.372%	$139.274	$139.27	$139.25	$139.30
Purchase #2	$160.55	7.870%	$173.1853	$173.19	$173.20	$173.20
Purchase #3	$198.68	3.511%	$205.6557	$205.66	$205.65	$205.70
Purchase #4	$103.49	12.659%	$116.5908	$116.59	$116.60	$116.60
Purchase #5	$78.34	6.436%	$83.382	$83.38	$83.40	$83.40
Purchase #6	$59.92	12.809%	$67.5952	$67.60	$67.60	$67.60
Purchase #7	$110.80	13.833%	$126.127	$126.13	$126.15	$126.10
7 purchase totals =	$845.22		$911.8100	$911.82	$911.85	$911.90