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	$68.30	5.619%	$72.1378	$72.14	$72.15	$72.10
Purchase #2	$20.26	4.681%	$21.2084	$21.21	$21.20	$21.20
Purchase #3	$85.38	11.205%	$94.9468	$94.95	$94.95	$94.90
Purchase #4	$68.56	6.345%	$72.9101	$72.91	$72.90	$72.90
Purchase #5	$82.45	10.788%	$91.3447	$91.34	$91.35	$91.30
Purchase #6	$17.86	9.300%	$19.521	$19.52	$19.50	$19.50
Purchase #7	$183.70	6.661%	$195.9363	$195.94	$195.95	$195.90
7 purchase totals =	$526.51		$568.0051	$568.01	$568.00	$567.80