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	$107.65	9.707%	$118.0996	$118.10	$118.10	$118.10
Purchase #2	$31.73	5.443%	$33.4571	$33.46	$33.45	$33.50
Purchase #3	$173.55	3.424%	$179.4924	$179.49	$179.50	$179.50
Purchase #4	$74.31	12.503%	$83.601	$83.60	$83.60	$83.60
Purchase #5	$198.28	8.533%	$215.1992	$215.20	$215.20	$215.20
Purchase #6	$16.93	12.716%	$19.0828	$19.08	$19.10	$19.10
Purchase #7	$139.73	9.116%	$152.4678	$152.47	$152.45	$152.50
7 purchase totals =	$742.18		$801.3999	$801.40	$801.40	$801.50