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	$67.85	7.794%	$73.1382	$73.14	$73.15	$73.10
Purchase #2	$74.75	5.155%	$78.6034	$78.60	$78.60	$78.60
Purchase #3	$155.45	13.835%	$176.9565	$176.96	$176.95	$177.00
Purchase #4	$183.44	7.244%	$196.7284	$196.73	$196.75	$196.70
Purchase #5	$62.91	3.264%	$64.9634	$64.96	$64.95	$65.00
Purchase #6	$16.72	7.185%	$17.9213	$17.92	$17.90	$17.90
Purchase #7	$183.66	4.393%	$191.7282	$191.73	$191.75	$191.70
7 purchase totals =	$744.78		$800.0394	$800.04	$800.05	$800.00