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	$142.78	7.780%	$153.8883	$153.89	$153.90	$153.90
Purchase #2	$176.90	8.186%	$191.381	$191.38	$191.40	$191.40
Purchase #3	$108.40	12.102%	$121.5186	$121.52	$121.50	$121.50
Purchase #4	$35.64	4.563%	$37.2663	$37.27	$37.25	$37.30
Purchase #5	$84.97	6.663%	$90.6316	$90.63	$90.65	$90.60
Purchase #6	$190.81	7.493%	$205.1074	$205.11	$205.10	$205.10
Purchase #7	$166.46	3.675%	$172.5774	$172.58	$172.60	$172.60
7 purchase totals =	$905.96		$972.3706	$972.38	$972.40	$972.40