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	$231.75	7.287%	$248.6376	$248.64	$248.65	$248.60
Purchase #2	$213.25	3.564%	$220.8502	$220.85	$220.85	$220.90
Purchase #3	$195.68	8.620%	$212.5476	$212.55	$212.55	$212.50
Purchase #4	$84.85	5.466%	$89.4879	$89.49	$89.50	$89.50
Purchase #5	$32.51	5.432%	$34.2759	$34.28	$34.30	$34.30
Purchase #6	$68.72	5.645%	$72.5992	$72.60	$72.60	$72.60
Purchase #7	$126.86	9.422%	$138.8127	$138.81	$138.80	$138.80
7 purchase totals =	$953.62		$1,017.2111	$1,017.22	$1,017.25	$1,017.20