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	$202.77	8.629%	$220.267	$220.27	$220.25	$220.30
Purchase #2	$106.68	9.378%	$116.6845	$116.68	$116.70	$116.70
Purchase #3	$43.81	3.588%	$45.3819	$45.38	$45.40	$45.40
Purchase #4	$103.57	7.622%	$111.4641	$111.46	$111.45	$111.50
Purchase #5	$174.48	7.620%	$187.7754	$187.78	$187.80	$187.80
Purchase #6	$179.45	4.506%	$187.536	$187.54	$187.55	$187.50
Purchase #7	$198.54	11.401%	$221.1755	$221.18	$221.20	$221.20
7 purchase totals =	$1,009.30		$1,090.2844	$1,090.29	$1,090.35	$1,090.40