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	$21.48	5.208%	$22.5987	$22.60	$22.60	$22.60
Purchase #2	$174.92	9.687%	$191.8645	$191.86	$191.85	$191.90
Purchase #3	$66.57	7.286%	$71.4203	$71.42	$71.40	$71.40
Purchase #4	$113.71	13.701%	$129.2894	$129.29	$129.30	$129.30
Purchase #5	$52.43	13.293%	$59.3995	$59.40	$59.40	$59.40
Purchase #6	$158.96	11.233%	$176.816	$176.82	$176.80	$176.80
Purchase #7	$46.78	8.311%	$50.6679	$50.67	$50.65	$50.70
7 purchase totals =	$634.85		$702.0563	$702.06	$702.00	$702.10