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	$92.49	7.578%	$99.4989	$99.50	$99.50	$99.50
Purchase #2	$72.59	6.728%	$77.4739	$77.47	$77.45	$77.50
Purchase #3	$42.78	8.473%	$46.4047	$46.40	$46.40	$46.40
Purchase #4	$220.36	3.823%	$228.7844	$228.78	$228.80	$228.80
Purchase #5	$238.76	6.422%	$254.0932	$254.09	$254.10	$254.10
Purchase #6	$187.40	11.446%	$208.8498	$208.85	$208.85	$208.80
Purchase #7	$117.78	6.782%	$125.7678	$125.77	$125.75	$125.80
7 purchase totals =	$972.16		$1,040.8727	$1,040.86	$1,040.85	$1,040.90