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	$131.40	12.533%	$147.8684	$147.87	$147.85	$147.90
Purchase #2	$58.86	11.415%	$65.5789	$65.58	$65.60	$65.60
Purchase #3	$232.60	7.684%	$250.473	$250.47	$250.45	$250.50
Purchase #4	$129.52	8.509%	$140.5409	$140.54	$140.55	$140.50
Purchase #5	$49.26	6.172%	$52.3003	$52.30	$52.30	$52.30
Purchase #6	$49.92	8.349%	$54.0878	$54.09	$54.10	$54.10
Purchase #7	$44.40	11.534%	$49.5211	$49.52	$49.50	$49.50
7 purchase totals =	$695.96		$760.3704	$760.37	$760.35	$760.40