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	$95.97	9.872%	$105.4442	$105.44	$105.45	$105.40
Purchase #2	$142.63	11.254%	$158.6816	$158.68	$158.70	$158.70
Purchase #3	$59.93	4.813%	$62.8144	$62.81	$62.80	$62.80
Purchase #4	$90.79	3.590%	$94.0494	$94.05	$94.05	$94.00
Purchase #5	$82.67	7.448%	$88.8273	$88.83	$88.85	$88.80
Purchase #6	$142.59	9.260%	$155.7938	$155.79	$155.80	$155.80
Purchase #7	$111.47	7.283%	$119.5884	$119.59	$119.60	$119.60
7 purchase totals =	$726.05		$785.1991	$785.19	$785.25	$785.10