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	$62.72	4.402%	$65.4809	$65.48	$65.50	$65.50
Purchase #2	$29.51	12.738%	$33.269	$33.27	$33.25	$33.30
Purchase #3	$62.32	5.284%	$65.613	$65.61	$65.60	$65.60
Purchase #4	$175.81	3.164%	$181.3726	$181.37	$181.35	$181.40
Purchase #5	$86.66	3.158%	$89.3967	$89.40	$89.40	$89.40
Purchase #6	$208.48	4.168%	$217.1694	$217.17	$217.15	$217.20
Purchase #7	$184.94	3.696%	$191.7754	$191.78	$191.80	$191.80
7 purchase totals =	$810.44		$844.0770	$844.08	$844.05	$844.20