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	$135.85	11.473%	$151.4361	$151.44	$151.45	$151.40
Purchase #2	$19.99	6.657%	$21.3207	$21.32	$21.30	$21.30
Purchase #3	$167.78	5.397%	$176.8351	$176.84	$176.85	$176.80
Purchase #4	$169.88	10.106%	$187.0481	$187.05	$187.05	$187.00
Purchase #5	$45.64	4.790%	$47.8262	$47.83	$47.85	$47.80
Purchase #6	$80.82	10.699%	$89.4669	$89.47	$89.45	$89.50
Purchase #7	$49.61	6.407%	$52.7885	$52.79	$52.80	$52.80
7 purchase totals =	$669.57		$726.7216	$726.74	$726.75	$726.60