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	$30.35	10.205%	$33.4472	$33.45	$33.45	$33.40
Purchase #2	$181.48	3.654%	$188.1113	$188.11	$188.10	$188.10
Purchase #3	$107.50	9.653%	$117.877	$117.88	$117.90	$117.90
Purchase #4	$198.42	4.527%	$207.4025	$207.40	$207.40	$207.40
Purchase #5	$40.60	4.767%	$42.5354	$42.54	$42.55	$42.50
Purchase #6	$89.41	9.579%	$97.9746	$97.97	$97.95	$98.00
Purchase #7	$154.69	6.346%	$164.5066	$164.51	$164.50	$164.50
7 purchase totals =	$802.45		$851.8546	$851.86	$851.85	$851.80